Pay API call

Hi,
to approve app Fundraiser X.com ask me:

"Can you clarify the 'Pay' API call that you are using to debit Donors' Preapproval Agreements please? Note that we will require the Project Owner / Artist to be the Primary Recipient of the funds with your site collecting its fees as Secondary Recipient (if you are charging a fee) so that the Project Owner / Artist is the Merchant of Record in the case of any Chargebacks or Refunds."

Who can give me the answer?