Difference in numbers

I have tapjoy integrated in one app and there in reporting you see the number of sessions. I also have admob interstitial at launch and also an admob banner.

Tapjoy shows 7000-8500 sessions per day, but I see ~3800-4500 banner and the same number of interstitial requests. (fill rate 99-100%)

Anyone faced with less numbers in admob? Or it is just tapjoy showing me big numbers?