STO GI and GR Difference

Dear Gurus,

My client have 30 plants, they use the weigh bridge scale to dispatch any thing via STO to another plant, some time qty is receive less and some time little bit high at the receiving plant due to nature of the product.

For the less I can receive less and charge the shortage to the cost center.

But how I deal with the excess, let say Plant A make a STO and GI for 1,000 kg and Plant B  received 1,020 kg, how I treat this in SAP, right now system don't allow me to receive more.

Kindly suggest.

regards,

imran khan