Automatically number subform lines, starting from 1 evertyime one is made

Automatically number subform lines, starting from 1 evertyime one is made

So i am currently working on a subform in an app. Like shown below the numbers in #Run should automatically populate. So when i add my first row the number should be 1. Adding a new row would mean that #Run would be 2. This should continue to whatever number of rows are inside this subform. When i submit a new form the counter should be 1 again in row 1.

I just can't seem to find a solution to this, hopefully i can find a solution through this community post.

Thank you in advance.