My 2 cents are not worth that even but here it is. It is your responsiblity to be closer that 100 pounds off if the buyer sends trucks he gets them and there 100 pounds off he has the right to return them maybe on your dime  , 50 pounds it happens 100 is way to far off someone made a big mistake. They should have been test weighted.  probably not what NAT wants to hear but I said it.