Unless I read it wrong, the rankings were on percent of capacity - which removes the "more seats to fill" variable from the equation, right? Those three schools still had the highest percentage of butts in seats.
No it was just based on actual attendance. There weren't very many hard numbers in the OP so it was kind of confusing. Here is the Top 15:
Top 10 Football Bowl Subdivision Attendance Leaders
1. Michigan:------------ 108,933
2. Penn State:---------- 107,008
3. Ohio State:----------- 105,261
4. Texas: ----------------101,175
5. Tennessee:----------- 99,220
6. Georgia:-------------- 92,746
7. LSU:------------------ 92,489
8. Alabama:------------- 92,012
9. Florida:--------------- 90,635
10. Nebraska:----------- 85,888
11. Southern California- 84,799
12. Oklahoma ------------84,778
13. Auburn --------------84,614
14. Notre Dame--------- 80,795
15. Wisconsin------------ 80,109