> With regards to the credit card payment, my guess would be that it went over a dual message system. Which means one message reserves the money, and a second one moves it.

Yes, it’s called an authorization hold or approval hold. The customer’s bank returns back with an authorization code or approval code reserving a certain amount of money. Then the merchant goes back with it to retrieve the amount actually wanted.

This is for situations like filling fuel, or hotel stays, or car rental where the final cost is not known at the beginning of the transaction, so an estimated amount is placed on hold, and then whatever is used is actually taken.