Add Row To Table and Changes Row Above Column Formula

Hello,

From the screenshots you can see that I'm trying to add an instance counter that displays 1 if it's the first subs in the table, a 2 if its the second sub and so on. 

The problem I'm having is whenever I add a new row, it autocorrects the formula above it to include the whole range. I want it to stay sequential so I get the proper count.

I'm all ears if there is a better way to do this or my formula/settings just need to be tweaked.

Thanks