Freight charges mentioned in PO at header level is getting apportioned based on quantity.

Dear Experts, Please confirm that my below understanding is correct?

Creating PO with header condition value (Freight or other charges - Group Conditioned). Now at Item Level, Material Price is getting apportioned based on quantity. But it should calculate based on Material Value, right? then only the Item, moving average price will be calculated correctly.

Kindly guide me on this ASAP.