You have the option to refund specific amounts or the full amount.
First, hover over the payment charge and you will see a drop down button appear on the right. Click the dropdown button and you will Refund as an option.
When you click the refund button you will two options. One for Full Refund and the second one for Partial Refund.
Full refund, as the name suggests refunds the entire amount charged to the credit card.
If you select Partial Refund and you will see an option to enter a specific amount you want to refund.
Once you have entered the amount, click Refund, and the amount will be refunded to the credit card charged.