Not as Good as I Thought

I received my averages for classes for the last three years, as compared to the full-time faculty and the other adjuncts. It is not quite accurate because I have been teaching a new version of the course that whole time and yet the advisors kept letting students who did not belong in.

Despite that caveat, it is still depressing.

I have a lower success rate by 22% than the ft faculty. I have a +.8 GPA in my classes though. How does that work?