Select places will place a pre-authorization on your card for an amount that is more than you are spending. It is entirely up to the merchant if a pre-authorization is placed and for how much. The pre-authorization reserves the funds, it does not claim the funds. Once the pre-authorization is released the funds will be placed back in your available balance and you will only be charged the amount you actually spent.
You will typically see this in instances where you receive the goods or service before you pay, like when using your Glint card at a gas pump, a restaurant, a hotel or when renting a car.
For any further questions regarding pre-authorizations, please submit a request from this page.