In correct planned Delivery cost

Dear Experts,

I have created one scheduling agreement with quantity 15000 with conditions basic price and delivery cost in percentage 1.65%.

Then I have scheduled 5000 quantity in it.

But when I take goods receipt of 5000 quantity the delivery cost is not distributing equally.

I am not getting why this is happening.

If I am scheduling 15000 quantity then delivery cost calculation is correct.

Please clear my doubt.

Thanks in advance.

Regards

Gitesh