This option is for option where module will not generate voucher code automatically, but it will get one voucher from already predefined list of voucher codes. Features that i will describe here are available under Price rules menu item. (predefined gift groups, predefined gift vouchers).
On list of defined gift associations (on moduel configuration page) you can define how the module will get voucher code that will be treated as a gift card code. As you already know you can:
Screenshot above shows where you can add predefined voucher codes to the list of voucher codes. Just hit the button to open a form where you can add new voucher codes to the list associated with selected group of codes.
You can manage predefined groups of codes and voucher codes under:
- price rules > predefined groups of codes
- price rules > predefined voucher codes