WIP Return issue

Hi

We have performed the WIP return for 24 QTY even though the Qty is not available in inventory and we not perform the wip issue as well.

Also we performed the account alias issue for that 24 Qty but for this work order X only 5 qty is required and 5 qty is available in inventory as well.

Here our question is?

1) How the system will allow this even though the Qty is not available, if its as standard functionality by oracle, how can i stop this or validate ?

2) we just made up $83000 in inventory for this work order X . When I checked in WIP value summary, all the material values,overhead and resource goes into negative