Adding records to subset based on counter reaching X number

What’s the best way of achieving this.

When a counter reaches X number.
Add record to subset.

When I add the new subset via the rule and save - I get this…

Subset appears in main subset page.
But appears as deleted on rules page.

Hi Simmeon, my name is Mark and I’m a builder at Netcall. I will send you my number if you wish to call, and I’ll do my best to help you out.

Regards - MP