Iterating rows in pairs

Is there an easy way to iterate rows in groups of 2?

I have an action that adds 2 rows to a sheet at a time and I would like to have each row behave like this:

row 1 1
row 2 1
row 3 2
row 4 2
row 5 3
row 6 3
row 7 4
row 8 4


I’m currently using a rollup to count and set column but because it’s more than 1 row at a time my iterations are off.

I do not understand what you are trying to do. Can you explain better?

Count unique submissions numbers