You may find that if you look at your Series Stats for a particular Series that the number of weeks counted is more than what is showing in your Race Participation Tracker.
In order for it to count in the Race Participation Credit Program, you would need to complete at least 50% of the number of laps completed by the class winner in your class car.
This is why it may count in the Series Stats but not in the Race Participation Tracker.
See http://members.iracing.com/membersite/member/Promotions.do for more information.