[Excel] Change the columns index from letter to number

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