Not sure where that was listed. Of all the games I have been to over the years, I have never seen it over 110K when I attended. Official attendance is always listed on the scoreboard in the fourth quarter and it's based on the number of tickets that were counted at entry points.
When I was at the Indiana game, official attended was listed on the scoreboard as 105K and change. For Michigan it was 106K and change. It will probably be similar for this game and possibly get close to the record. The largest attendance on record is just over 110K for a game against Michigan a while back. You can stuff more in technically. But that's about the max you can fit in there without violating safety codes.