A sales number (or sales key as it is sometimes called), is a temporary number that does not have an expiration date. Your product's protection period only starts once your sales number is registered and is replaced by a license number.
You can install your product with a sales number, but you need to register it within 30 days after installation (otherwise the program stops working). Click here to register your sales number.
(Partners can register sales numbers for their customer from the Partner portal - click here.)