Apple policy on hardware purchases is that your credit card is not actually Charged until the new device Ships.
What does happen is a temporary authorization, to improve the chances that when the final transaction hits your credit card account, it is more likely to be paid.
For most credit cards, this puts a temporary hold on that much of you credit line until one of:
• the charge goes through in the same or slightly different amount, or
• the transaction is Actively cancelled (this is rare) or
• the transaction times out without being completed.
The temporary authorization will be removed once any of those happens.
Timing out can take a few days to a week for most cards, but this is a policy of the credit card issuer, not Apple.
This operating model is loosely based on a restaurant-type transaction:
your preliminary bill is calculated, and you present your card to pay it.
a temporary credit card authorization is processed to hold money for the final payment.
the authorized slip is returned to you, and you might amend it by adding a tip, or possibly add another drink.
Some time later (minutes to days, depending on accounting practices) the final transaction goes through and your account is actually charged.