When you open a spreadsheet by defautl the columns are indexed by letters:
But if you want to change the format and put the index in numbers, here's how:
- Open your spreadsheet
- Click on the orb button
- Click on Excel Options and move to the Formula tab.
- Go to the "Working with formulas" section
- Check the "R1C1 reference style"
- Note that: Upon hovering your mouse cursor on it, you shall get all the information about this feature.
- Click on OK