you have to change your data structure by using one field (column) for week1, week 2, and progression of followers separately. The last field with be a function that runs the calculation.
Airtable does not handle running totals well. If you only want the difference, you can link each record to its predecessor and calculate the difference. However, that is a lot of linked relationships to maintain. You can also use a script to calculate a running total. There is an example script in the docs.
