The amount that appears in the "Related Transactions" section is the amount of the refund check that is applied to the credit memo / linked to the credit memo. In your case, for some reason that amount is $605 instead of $765.
This can happen for a variety of reasons. For example, if you decrease the CM amount save it, and then increase it again to a larger amount. After doing that, the refund check will only be linked for the lesser amount. Similarly, if both the credit memo and refund check were smaller, then if you first increased the CM amount and then the check amount, they'd still be linked for the original amount.
To resolve this, open the Receipt Payments window, select the customer, and then find the refund check in the list of open things to "pay". Click on it, and then click the Discounts and Credits button at the top of the window and then select the credit memo you want to link the check to. Then save and close the windows.
