I was surprised too and even asked him about it, and he ensured me the numbers were correct. That could also just be the number of tickets that were purchased and scanned before the event and not walk-up buys on the day of. I'll ask him again next time I see him.
Also, when you say backwards, are you asking if I got the actual digits backwards, or if I mixed up the numbers between the tours.
08/08 - Slipknot/Lamb of God
09/30 - Revocation
10/04 - The Black Dahlia Murder
11/12 - Kataklysm