I would like to ask a question : Is there any reason why the incoming clicks number is lower than the actual number?

I've set virtual("/te3/in.php"); on every my pages, and te3 worked very well before. But recently, I got lower incoming click number than reality (the number from trafficholder, and I also count my access log with the GET request, so this number should be absolutely correct)?
Do you guys could give me some clue?

With Best Regards,