Transaction quantity must be less than or equal to available quantity

Hello Everyone,

I have a situation, where one of the user has transfer X number of quantities from Subinventory FGD (Finished Goods) to QAR (Quarantine). Now when the user tries to do the subinventory back to FGD, it throws message "Transaction quantity must be less than or equal to available quantity".

Under QAR, the Total quantity shows X,

Available to Reserve = 0

Available to Transact = 0

Setup of the 2 inventories:

FGD: All the below options are checked:

Qty tracked, Allow reservations, Include in ATP and Nettable

Whereas, for QAR, only below options are checked:

Qty tracked

So, I'm wondering where can this X quantity go when it is not being used anywhere else from QAR subinventory?