If you are it’s looking for the current month’s current count after each flow process, you can create Environment Variables. So, something like this:
‘Run flow (get count of forms during this flow.
Get Environment Variable %LastFlowRunMonth%
Set variable %ThisFlowRunMonth%
If %LastFlowRunMonth% does not equal %ThisFlowRunMonth%
Set Environment Variable %LastFlowRunMonth% to %ThisFlowRunMonth%
Set Environment Variable %MonthlyFormCounter% to 0
End (IF)
Get Environment Variable %MonthlyFormCounter%
Set Environment Variable %MonthlyFormCounter% to %MonthlyFormCounter + Forms.count%
good luck!