Having trouble deciphering your math, but it sounds as if you acknowledge being undercharged at checkout and then think because it was settled that you are not responsible for the difference. Were there charges that for whatever reason had not yet made it to your folio? That happens frequently. Just because you happen to check out faster than the charges post doesn't mean that you are not responsible for them. However, I would call the hotel and ask them to fax or e-mail you the final receipt. It should have the charges itemized. Then you will be in a better place to dispute any charges.