During your Magento setup, a default discount item is configured. This discount item is used for all discount amounts that are not explicitly mapped from a Magento coupon code.
To explicitly map a Magento coupon code, go to Setup > Customization > Record Types > Magento Discount Item Mapping > View Records. This record type supports a mapping between your NetSuite discount items and your Magento coupon codes. If mapping new entries or changing existing ones, please be sure to refresh integration caches when you are finished.
Important: The connector will convert all coupon codes from Magento to lowercase, so make sure you enter all lowercase characters in the Magento Coupon Code field.