To exclude gift cards from earning criteria of the business,
- Create a new Line Item Selector > select Operator as "is" > Line Item Type as "S". [S is for Service Charges which includes Gift cards].
- Create new Qualification criteria > In the Line Item Filters, select your Gift card line item selector and select Exclude from earning.
- Select Processing Functions as "Sum of Amounts".
- Update the Changes made.
- In the Cockpit, add the QC to the Earning qualifier of the Business.
I would also recommend to run a test transaction and check if everything is configured correctly.