Can't edit PayPal payments?

It looks like the edit payment option is present but it is not there for payments that go through PayPal. I want to mark how much of the transaction went to PayPal fees. ...or is this done automatically?

I need to edit a payment in Zoho Invoice and can't see how this is done now. I checked the help and there is this page:

http://www.zoho.com/invoice/help/invoices/online-invoice-payment.html

The screenshots they show are outdated.

Thanks.