The requested refund amount for the shipping fee is too high. For help on how to proceed, see http://sellercentral.amazon.co.uk/gp/help/25181
This error occurs when the refund amount you are requesting for the shipping fee component of an order exceeds the amount that can be refunded. Common reasons why your requested refund might be too high include the following:
For example, if a customer pays £20 for shipping, you can refund up to £20 toward the shipping fee. If you refund £15 of the shipping fee, the customer's shipping fee balance is £5. Any future refunds for the shipping fee cannot exceed that £5 balance.
To view the current balance for any component in an order, you can search for the order using the Search Orders feature in Seller Central.
To resolve this error, please resubmit your data with a refund amount that is less than or equal to the customer's current balance.