Is this the correct behaviour?

I have two users set up, myself and a fake person so I can test auctions etc. I have a house % of 10% set.

When I win an auction as User A, I go to pay as per normal using the Paypal Sandbox. I assume after this the 10% is taken from the winning bid.

However when I log in as User B, I am instructed to pay the 10% as it is outstanding. Should this 10% not come out of the winning bidders payment?

As far as I understand it, the house commission is deducted from the winning bid at the Paypal stage and the Adaptive Payments should theoretically send 10% my way. In other words, the seller shouldn’t have to pay 10% upon the successful sale via a separate payment. They could opt to not bother and still receive the funds (presumably minus the 10%).

Can someone clarify this for me as it is potentially a major issue.

Thanks
Peter