Yeah maybe it was a bigger discrepancy, or maybe they only screwed up a small part of the tax formula. I can't really remember but I definitely remember the shock when the amount they were asking for in person was different than what was on the invoice and thus difference than the amount of the cashiers check I brought in. I'm just going from memory though so I could have some of the details wrong. Hopefully someone else can chime in with the specifics of what you should be charged. In any case, it seems like the type of question the service center should be able to answer if you just ask them.