There is no parking fee for any
DVC reservation at VGC. However, your issue has been mentioned before and MS, when contacted, has asserted that it is just a generic message given for all reservations at VGC (in other words, just another built-in website failure among the hundreds that have also been previously mentioned). Nevertheless, to be sure you are not charged, either at check-in or sometime after, you should consider checking with the front desk to assure you are not being charged.