Giving Claude 7,000 rows of Excel: it caught a double-count

A 7,341-row sales log

Remember the bubble tea shop's sales log of more than 7,000 rows from Mark's aunt in video 301? This time we give that exact file to Claude, and every table and chart you're about to see is a real Excel file it made.

SETUP

An add-in inside Excel

To use it right inside Excel, install the Claude for Microsoft 365 add-in from Microsoft Marketplace, then go to the Home tab, choose Add-ins and click Claude. The add-in runs on Excel for the web, Windows and Mac, and needs a paid plan, Pro or higher.

CATCHING ERRORS

What's the real total?

The first question was the total revenue for three months, and Claude didn't just add up the whole column, because it noticed three monthly total rows mixed into the data. Adding everything would give almost 587 million, double the correct figure of 293 million.

SUMMARY

By item, by month

Next, ask it to summarize revenue by item and by month, color the items going up and down, then draw a column chart. Taro milk tea fell 57 percent, while peach lemongrass tea rose 42 percent.

FORMULAS

Change a number, it recalculates

Then ask Claude to build an October forecast sheet with formulas, with one growth-rate cell for peach tea. Change that cell from 5 to 10 percent and the forecast total jumps from about 96 million to nearly 97.3 million, because the formulas stay intact instead of being overwritten with numbers.

CAREFUL

Work on a copy

According to Anthropic's guidance, Claude asks before overwriting data and can't do macros yet. Work on a copy, and only open files you trust, because unfamiliar files can hide instructions.

SAY IT ONCE

The Instructions box

In the add-in's Settings there's an Instructions box where you write your habits once, like using dots as thousands separators, so it does it your way every time.

PART 3

Next: PowerPoint

Part 3: take these results straight into PowerPoint as a five-slide staff meeting deck, without copying a single number.