Open stock-negative stock reversal

Dear experts,

Currently I am trying to migrating open stock

1)Migo  561 stock goes to storage type 998 +ve

2) LT06 movement type 999 stock goes to - ve

3) LT10 offset the stock 998 using movement type 999 migration  done

Now my question is step 2 if I wrongly migrated for example qty is wrong want to reverse it, how to reverse or cancel

Please advise

Regards

Raj