It's a simple pre-authorization. The money is being "saved" to spend later on the item when it becomes available. The seller puts a hold on that amount of money on you credit card and that amount cannot be used then for anything else. It, in effect, reduces your available credit for the time the money is held. If you have a $1000 credit limit and $400 is held in reserve, then you only have $600 to spend else where until the reserve is charged and then paid off. You have not been charged the $400 that is in reserve, as in you do not yet owe it and it will not accrue interest until it has been charged to your account, but it's locked up and you can't use it for anything else either. But, gee, 8 or 9 months seems a very long time to have your money tied up in limbo.
Shylaah