Allowing to Attach more than available quantity in work order parts list

Hi,

We are facing an issue.

We are creating a work order parts list manually.

When I attach parts list manually it is allowing us to attach more than available quantity for the item & lot from secondary location.

For eg. Component item number = RM, Lot number = LOT1, On hand = 20 KG. Available qty = 20 KG.

When we manually attach Component RM & LOT1 against the work order, it is allowing us to attach 22 KG against work order.

Also it is allowing to issue that quantity in super back flush.

In P31113 we have set negative quantity on hand = 1

Can you please help me to identify why it is happening and how to prevent it.