A threshold limit of $50 has been set, but the user can fill gas in some stations for more than $50. Why?
CardValet controls are only invoked during the authorization of a transaction. In some cases, such as Gas Stations, a card may be tested for validity by doing a $1 per-authorization, and the actual transaction amount is charged to the card after the transaction. Some gas stations will do as a pre-authorization for a maximum amount, e.g. $126, and some gas stations will check validating, e.g. $1. In the latter case, the actual transaction amount may exceed the limit, while in the former case, an authorization may be denied.
