[Freeswitch-users] custom call counter

Hi, Instead of using "show calls count" to obtain the current call count stat, I am writing some C code to increment a counter during on_answer_hook and decrement the counter during on_hangup_hook. It looks like my counter result is very closed to "show calls count" when the traffic is low, like 50 -60. But when traffic is high, like 1000 calls, my counter is showing 30% less. When all calls are finished, my counter becomes 0 again, and that proves that it does not increment/decrement more than it should. Is this normal? Does anyone have any idea why there is such discrepancy? thanks, jb