How do I correct an Invoice without impacting Quantity

I have a PO with Qty 10 and Price 10 for Total $100.

A receipt has been record with the same Qty and Amount.

The Invoice came in as $110 where a $10 freight charge was applied which was not reflected on the PO.

When the Invoice was match to the PO, the system automatically put a $10 Price Variance Hold.

Later the supplier sent a -$10 credit for the freight charge and we would now like to create a credit memo for $10 and link to the invoice.

In the Correction window I have the option of performing a Price Correction, however when I do this I am also forced to adjust the Qty since it is a mandatory field.  I don't like this option since it will mess up the Billed Qty vs. PO vs Rct Qty which is all correct as-is.