Paypal is going to forgo the $0.30 cents (that they use to charge in the past with refunds) but keep the original 2.9% of the transaction amount they charged originally.
https://www.paypal.com/us/webapps/mpp/ua/upcoming-policies-full
We’re changing how we treat refunds. If you refund (partially or fully) a transaction to a buyer or a donation to a donor, there are no fees to make the refund, but the fees you originally paid as the seller will not be returned to you.
These changes will go into effect on May 7, 2019. If you agree to these changes, you don’t have to do anything. If you don’t agree with these changes, you may close your account. If you close your account before May 7, 2019, the changes will not apply to you.