Interesting. In your case, and i've done what you've done once last year, it should be 4. However, to answer your specific question, I'm going to assume it's the add-ons that are charged for non SE members that are charged for certain destinations. Perhaps they pay the $500/$750 and then do a chargeback? Then AC kills all of your eupgrade credits? As far as how much leeway? No idea, have never paid these surcharges.