I think there is a problem in the drive charts. I've actually noticed that a few times, but this time I'm sure:
Example :
http://mfn2.myfootballnow.com/box/2778New England had 5 tries on 4th, and succeeded on 2 of them. That means they should have 3 turnover on downs. They only have 3 while I have 1 of them in my column.