You can call and ask, but, again, based on my previous experiences with them, macconnection, like Apple, will do a pre-authorization, but not actually charge you until it ships.
Be very careful if you are using a debit card or a card close to the credit limit. If you get 2 pre-auths at once, you could be out of that much money until they expire. The money is not actually taken out of your account, but it's sort of "reserved" for a few days until it disappears or they push the charge through.
The actual real charge will happen when it ships.