How do I handle the Shipping Cost that the Customer Paid to Return the Board???  

We sold 100 boards @ 62.00 each.  (No Shipping Cost on Invoice)

Problem:    Customer returned one of the boards and took credit for the cost of the board which was $62.00 + $7.49 for the shipping cost that the customer paid to return the board (which was not part of the original Invoice) = $69.49

Resolution:   Create a Standard RMA for the Cost of the board $62.00 and since the shipping was not part of the invoice you will NOT be able to included that cost on the RMA, so you will then need to Create a General Credit Memo for the shipping cost of $7.49 and then use that CM in the AR Offset module to apply against the Invoice.