The DISCOUNT ACCOUNT field is the general ledger income account that will be used when creating any new discount items in your accounting system. This will only be used if a new discount item is created, it will not affect any existing items in your accounting system. If you do not select a DISCOUNT ACCOUNT, then a default account will be created for you.
The name of the default account will be "Discounts Given" and the sub type will be "DiscountsRefundsGiven". If you already have an existing account that has the same name as our default, then that existing account will be used and a new one will not be created.