The 15,232 number is correct - the last Rally in the Alley game. This was the game where Joe Raymond gave the pre-game speech to the team and basically landed the head job when Torbush bolted for Mack Brown's staff at NC.
I couldn't figure out where the 53,000 number was coming from and then remembered we had played at Texas A&M the following week. Sure enough, 53,779 was the attendance for that game in College Station. At some point, someone from Tech incorrectly pulled that number.