The only rule that the NCAA has is that two players can't be on the field at the same time with the same jersey number. Back when Major Applewhite was at Texas, there was someone on defense with #11, too. That's when I first heard about the rule.25. How is it possible for Ohio State to have two number 2's on the field? I know they don't play at the same time, but Terrelle Pryor and Malcolm Jenkins both wear number 2. I can't think of where I've ever seen that before.
And what Ramy said too. When you see team pictures that include walk-ons many of the numbers are repeated. The number of scholarship players is capped at 85, but many teams have 20-30 walk-ons.
In the first row you can see two 8's, two 9's, two 11's, and two 12's.