Every public comment an AGENT sends is counted as ONE public comment.
This is irrespective of the number of tickets. It's just a simple count of how many public comments an agent has submitted during a given period of time.
That way, if an agent sends 10 public comments on 1 ticket, their total public comments will be 10. If they send 10 public comments on 10 different tickets, their total is 10 as well.