But seriously, what a tard. You'd think he would know that he'd be caught eventually. If he was smart, he would use a washable marker and only change those numbers when he went driving and knew he was going to speed, so he could get rid of that evidence when he got home. Even with that, though, it's still a pretty dumb thing to do.
If you wanna speed, go find a back road that nobody uses and speed your heart out. Doing it out in the open is just asking for a ticket.