I'm getting the same thing. I haven't found an answer yet but my best guess is that they are also including any time the game is in stand-by. In other words, if you don't press start on the game while you're on the home screen, and quit explicitly, the game is still running in the background (which is what allows that super fast switching.) It's still counting all of that time. Mine, right now, is saying I've played 6 days.
Yeah I have this problem too. Would love to see this fixed in the next update.
For some reason its broken on that game, lol Mine says i played for 20 days, that was 2 days after i got the game.
Camped out at Best Buy (Dec. 17-18th 2005) 5th in line for 18 hours. Got a Premium! Warranty's Are nice!