Only you know if the email address aligned with your Paypal account is the same one you use in your RCUniverse account.

The comment box below the Paypal option in the invoice is a free text field and is used by sellers to provide any last minute information or comments to the buyer.

The field in which you list your Paypal email address is located in the ad creation tool on Step 3 where you select your accepted methods of payment. There is a small field directly below the Paypal option on that page where you enter your Paypal email address, which as stated above, only you would know if it is the same as the email address you use in your RCU account.