Invoice qty greater than the PO qty

Hi All,

I have created material  PO with 100 qty Value 5000 and freight cost 1000 rs for the same Qty.

Issue: at the time Freight Invoicing with PO/bill of landing

Material: GR & IR Done for 100 qty -- No issue

Freight: when am doing invoice (MIRO) i have given Purchase Order no and paid the freight rs 1000 for whole 100 qty

Issue: If i do invoice (MIRO) by for the same PO and given bill of landing, system still proposing some qty 40 Qty and proposing some cost.. and able to save .

but it should not propose the Qty... Plz let me know how to restrict it... In case freight Invoice

Thanks