Quantities Grid; Available field (Required for Work Ticket)

Is there a way for the Available field to automatically take into account the "Req for W/T" quantity?    It seems completely illogical that the On Hand Quantity is the same as the Available when parts are needed for an open Work Ticket.    

I mean it takes into account On SO and subtracts out those quantities.   Why wouldn't it subtract out Req for W/T the same way?

Is there a setting or something we are missing?