PayPal is improving the refund system, and clarifying the way partial refunds will display within the transaction. 
 
Beginning in mid-August PayPal users will be able to issue multiple partial refunds on payments they receive, up to the total amount of the original payment. In addition, payments that have only been refunded in part will display a status of "Partially Refunded" instead of "Refunded" in Account History.

As always, all refunds must be completed within 60 days of the transaction, and users who issue multiple partial refunds will only be charged a transaction fee based on the payment amount received and not the funds that have been refunded
 
Go to PayPal to read all about  PayPal Refunds and Partial Refunds.