It looks like the 85.63 is just a temporary authorization or hold that the pump makes when you tap your device in order to let you start filling your tank (it's sort of a precaution, the gas station just wants to be sure there is up to a certain amount of money on your debit card before they let you start filling to make sure they get paid at the end). It's standard procedure, similar to what's done when you take a cab or check into a Hotel, since they don't know how much they're finally going to charge until later on. That being the case, the 85.63 should be canceled automatically within no more than a few days and only the 11.50 you actually bought will end up being charged to your bank account. Just check your statement to make sure. If you end up being charged more than 11.50, contact your bank and also report the issue via Wallet, as welafever suggested.
Note that Wallet doesn't always update transactions, so the 85.63 may remain on your Apple Pay recent transaction list in wallet, but shouldn't appear at all on your bank statement.