When reimbursing you for a buyer refund, Amazon determines the amount of the order-related fees that are credited back to you and the amount of such fees that Amazon retains, based on the item's product line and the order amount.
Refunding Book orders
When you issue a full refund for a product, Amazon will refund all of the original order-related fees. When you issue a partial refund for a Book product, Amazon retains the variable closing fee and credits you a proportional amount of the referral fee originally charged for the order, based on the percentage of the item price you refunded to the buyer.
For Individual sellers, Amazon also retains the R$2,00 fixed closing fee. (This fee is waived for Professional sellers.)
For sample calculations, see Partial Refunds for Book Products.
Refund Credits and Administration Fees