Let the spreadsheet do the math and the assistant write the words

Most monthly reports end with a few paragraphs under the table: what went up, what went down, what missed its target and why. Sales by region, budget against actual, a program’s indicators for a funder, support tickets, enrollment: the table tends to be ready days before anyone writes the words, because writing about numbers is slow and nobody wants to get one wrong.

A chat assistant can write those paragraphs, as long as it does none of the math. So split the work. The spreadsheet calculates every change and percentage. The assistant turns those finished monthly numbers into sentences, tags each one with the row it came from, and asks you about causes instead of inventing them. By the end of today you’ll have this month’s commentary drafted and checked, every number traceable to a cell, and a table and a prompt ready for next month.

What goes wrong when the assistant does the math

Paste raw figures into a chat, ask for “a commentary on this month’s results”, and you’ll get fluent text. The problems are the kind you only see when you check:

• Arithmetic. A language model produces text a piece at a time; it doesn’t calculate the way a spreadsheet does. A percentage can come out right once and wrong the next time, and a wrong figure reads exactly like a right one. Some assistants can run a small program to do the math on a file you upload, which helps, but then you’re checking code you didn’t write instead of formulas you can see.
• Rounding and units. 12.54% becomes 12.5% in one paragraph and 13% in the next. Occupancy that went from 78% to 71% is reported as “down 7%”, when it fell 7 percentage points, which is a drop of about 9%.
• Direction. A rise in complaints or refunds gets described as growth.
• Causes with no basis. “Thanks to strong demand” or “due to seasonal factors”, when nobody said a word about demand or seasons. Watch for this one most, because it sounds like analysis.

Build a commentary table

Add a tab to your report with one row per metric and eight columns: Metric, This month, Last month, Change, % change, Target, Vs target and Better when. With the metric in column A and the first one in row 2:

D2  Change       =B2-C2
E2  % change     =D2/C2   (format as a percentage, no decimals)
G2  Vs target    =B2-F2
H2  Better when  type "up" or "down"

Fill the formulas down to the last row. A few details save trouble later:

• If last month was zero, the % change cell shows an error. Type “new” there instead.
• For a metric that is already a percentage, such as occupancy or on-time delivery, leave % change empty. Its Change cell then shows the difference in percentage points (78% to 71% shows as -7% in a cell formatted as a percentage), and the prompt below tells the assistant to say it that way.
• Format every cell the way it should read in the report: whole percentages, thousands separators. When you copy cells into a chat, what gets pasted is usually what the cells display, so the assistant sees 20% rather than 0.2033898.

For anything beyond subtraction and division, such as a year-to-date total, ask the assistant for the formula and put it in the sheet, where you can see it (Describe the formula you need in plain words shows how).

Under the table, write your notes: what happened this month that the numbers don’t show, such as a price change, a holiday, a colleague on leave or a system outage. One numbered line each; these are the only causes the assistant may use. If you keep a running log during the month, most of them are already written.

The prompt

Start a new conversation, paste this prompt, then your table and your notes where it says so:

Below is a table of this month's figures, already calculated, and my notes about the month. Write the commentary for my monthly report.

Rules:
- Describe only the figures in the table. Do not calculate anything: no new totals, averages, differences or percentages.
- Copy every number exactly as it appears in the table or in my notes.
- After each sentence, name the row it comes from in square brackets, for example [Revenue].
- The column "Better when" says whether a rise is good or bad news. Follow it.
- For metrics that are already percentages, describe the change in percentage points, using the Change column.
- For counts under 20, give both numbers instead of the percentage.
- Explain a change only with one of my notes, and cite it, for example [note 2]. If a change is large and no note explains it, do not guess: put a question about it in a list at the end.
- Start with the metrics that missed their target.
- Plain paragraphs, no headings or bullet points, at most 180 words before the questions.

Table:
[paste the table here]

Notes about this month:
1.
2.

Before you send it, look at the pasted table. If you see long decimals or a missing column, fix the formatting in the sheet and copy again. Monthly figures are often internal, so use the assistant your organization has approved for them; if you’re not sure which one that is, Before you upload a client document lists what to check.

A worked example

For example, here is the table for a small training center comparing September with August. The center and its figures are made up.

Metric	This month	Last month	Change	% change	Target	Vs target	Better when
New enrollments	142	118	24	20%	150	-8	up
Certificates issued	96	104	-8	-8%	100	-4	up
Room occupancy	71%	78%	-7%	(empty)	75%	-4%	up
Revenue	31,400	27,900	3,500	13%	30,000	1,400	up
Refund requests	9	5	4	80%	6	3	down

Notes:
1. Evening course fees went from 180 to 200 on September 1.
2. A weekend course with 30 places started on September 13.

A first draft written under these rules might end with questions like these:

1. Certificates issued fell from 104 to 96. Did fewer courses end in September?
2. Refund requests rose from 5 to 9. Did they come from one course?
3. Did the 30 weekend places lower the average room occupancy?

Answer the questions, then ask again

You know the answers, or know who to ask. Add one line per question to your notes, then send: “Here are notes 3 to 5. Write the commentary again with the same rules.”

3. Two intensive courses ended in August; none ended in September.
4. Four of the nine refund requests came from the Tuesday spreadsheet course, which moved to Thursdays at short notice.
5. Yes. The weekend course was half full in its first two weeks.

The second draft could read like this:

Certificates issued fell 8% to 96, 4 short of the target of 100 [Certificates issued], because two intensive courses ended in August and none in September [note 3]. Room occupancy fell 7 percentage points to 71%, 4 points under target [Room occupancy]; the new weekend course added 30 places and was half full in its first two weeks [notes 2 and 5]. Refund requests rose from 5 to 9, above the target of 6 [Refund requests]; four came from the Tuesday spreadsheet course after it moved to Thursdays at short notice [note 4]. New enrollments rose 20% to 142, still 8 short of the target of 150 [New enrollments]. Revenue rose 13% to 31,400, 1,400 above target [Revenue], with evening fees at 200 instead of 180 since September 1 [note 1].

Check every number

With the table beside the draft, go through it once:

• Find each number in the table or your notes, in the row the brackets name. A number you can’t find is a calculation the assistant did on its own: delete it, or add it to the table with a formula and ask again.
• Every “rose”, “fell”, “above” and “below” should match the sign in the table, and every cause should come from a note you wrote.

Keep the tagged version in your files, and delete the brackets by hand in the copy that goes into the report.

When you don’t need the assistant

If your commentary says the same thing every month with different figures (“Enrollments rose to 142, 8 short of target”), skip the assistant. A formula can join text and cell values into a sentence that never miscopies a number, and the assistant can write that formula for you once. The assistant earns its place when the story changes from month to month.

Try it today

Build the commentary table for this month’s report, with your notes. Run the prompt, answer its questions in one line each, and check the second draft against the table. You’re done when every number in the draft points to a cell you can see. If this month’s figures aren’t in yet, run it on last month’s report: the table is the same, and you’ll learn how the prompt behaves before a deadline depends on it. Write down when you started and when you finished; next month, with the table and the prompt saved, you’ll have something to compare.

Next month, and the next step

Next month the table is already built: copy the This month column into Last month, type the new figures, and the formulas do the rest. Save the prompt with your others (Keep your best prompts in one place). If collecting the figures is what takes hours, A monthly summary you build once and refresh each month sets that part up once, with a pivot table.

If the commentary is headed for a meeting, each sentence you checked today can become the headline of a slide: Write the headline of every slide before you design any of them builds the storyline from there. When the whole report needs presenting, Turn a long report into a ten-minute presentation walks you through it step by step.