It is recommended that you let SPBAS handle license key string generation. 

However, in some situations such as boxed software you might have a predefined list of license key strings to use. In this case, you would need to enter your list of keys. As orders are placed the list of keys would be consumed. Once all keys are consumed, no more licenses will be issued.

If SPBAS handles license key string generation then as each order comes though a license will be created.