When creating a redeemable, if you first select an Existing Qualification, then switch to a Flat Discount, the previous Existing Qualifier will still be attached to the redeemable. The Existing Qualification will need to be removed, as this will not happen automatically when switching to Flat Discount or New Qualifier.
When an Existing Qualification is attached behind a Flat Discount, the discount will pass through the Existing Qualification and apply as per the criteria, not the flat discount.
To do remove the Existing Qualifier, click the "x" found all the way to the right of the Qualifier selected.