Subcontracting 542 challan correction

Need a help to resolve this issue on Subcontracting

Out client used to send 1000Kg of material A to the subcontracting vendor with challan and take back unused material A at year end .

Sap process

1.541 TP to sub con vendor for 1000 kg

2.create Challan for 1000 kg (J1IGSUBCON)

3.PO to sub con vendor with component 800 kg

4.GR with component consumed 800 kg

5. Reconcile Challan for GR doc and 800 kg is reconciled (J1IGRECON)

Now the Sub con vendor says they have unused material of 200KG and asked to take back .

So we did a 542 and took back 200 Kg .

Now how to reconcile the Challan ?

in system Components issued is 1000 Kg and Consumed (recolied is 800 kg) . the 200 Kg is not reconciled. What is the best practice to correct it