Maximum Quantity in Supplier Programs - Eligible Products

We have set Maximum Quantity in Supplier Programs under Eligible Products area for specific Product but it does not work

Lets say

Item A - 5% Discount and Maximum Quantity = 10

Raised PO for 20 Quantity and received 20 Quantity but rebate is calculating on 20 Quantity but it should calculate for 10 Quantity only

Is this standard Behavior or do i missing any setup