excess stock clearing

Today i have received 1000 mtrs of cloth from vendor i kept it in stock with 1001 batch...

after that i have issued that to production only 500 mtrs...with 1001b1 batch...

later on only i came to know that actually only 800 mtrs only i have actually received frm the vendor..but in system now will show 500 mtrs balance in 1001 batch...actually only 300 should show..

how to reduce the balance 200 mtrs...

this happens everytime bcoz my client wont chk the quantity by the time they receive the material after issuing 2 or 3 batches only they will chk..

how to reduce the stock every time...