You can store a list of product unlock codes in Vendor Control Panel > Manage Products > Delivery Options. The system delivers one of the codes to a customer after purchase. Check the box Provide a Code and select "Choose Codes from a List" option setup the delivery method.
In stored codes, each line is an individual code. After purchase, the system picks the next available code from the list and sends it to your customer via email and the code is then removed from the list. If the number of remaining codes is down to the Alert Number you set, the system sends you a notification to remind you to input more codes to ensure future customers are able to receive their codes after purchase.