Thanks for your post and welcome to PayPal community!
Partner fees are seller fees assessed by the website an item is sold from and are not part of the fees for using our services to receive money. I am very sorry for any confusion this may have caused you, and the best place to look for the terms for this fee and how it is totaled would be on the service you used to sell the item. It's a pretty common practice for most selling services because it allows them to deduct their fee with each item sold instead of a separate billing.
I received several transactions for sales at Discogs in February, Paypal has detained Discogs fee on each of those transactions, now Discogs demands payment for the February invoice! where is my money?
