Return eligibility is applied per item, not per order. If your order contains items purchased at different discount levels, each one is treated separately.
For example, in a single order you might be able to receive a refund for a full price item, store credit for an item purchased at 35 percent off, and nothing for an item purchased at 60 percent off, because that item is Final Sale.
When you open the returns portal, eligible items will be selectable and Final Sale items will be shown as not eligible. This is not an error.
The $21.95 processing and handling fee is charged once per return, not once per item.