There are two steps in any credit card transaction. In the first step, the charge is "authorized" by the issuing bank. In the second step, the amount is "captured" and the transfer of funds is finalized by the payment processor and banks. On your debit card, you will see the "authorization" show up and reduce your available balance. If the charge is not "captured" then the bank will release those funds back to you and your available balance will go back up by that amount.