What do you mean by “ascending auction” and “descending auction”?
After the ascending-bid phase comes the descending-bid phase. In that phase, we state a descending amount, which is added on top of the highest amount from the ascending-bid phase. The descending amount then decreases in steps until it reaches the highest bid from the ascending-bid phase.
If someone presses Accept during the descending-bid phase, that person is the buyer, subject to awarding.
The personen accepting the bid pays the ascending-bid amount, the descending amount and the additional costs stated for the auction. They must also pay any stake premium.
If no one accepts during the descending-bid phase, the highest bidder in the ascending-bid phase remains the highest bidder. However, no rights can yet be derived from this, because all auctions are offered subject to awarding.