Discounts in GrowthZone work differently than discounts in QuickBooks. Synced invoices with discounts will appear in QuickBooks with a negative line item for each discount. 

1. Create discount product/service in QuickBooks.  Use Intuit's QuickBooks Support for questions on how to create a discount.
2. Create Discount Types and Discounts in GrowthZone. See Working with Discounts for more information.  
3. Complete mapping.