admin commission

Hello,
from what I understand the admin commission(Amount is in percents. Enter amount without % sign ) for project funding is the repartition between the project creator and the admin.
however using WEpay, if I put 5, the donator for 10$ is paying 15,59??
If I put 9 , the donator is paying 19,59, if I leave it blanck the doctor is paying 10.59.
Normally the donator doesn’t have tp pay the admin fee, but the project creator???
however this is not %, please advise.
thank you