Logic of screen "Item Supply/Demand"

In our business process setup, we always specific the sub inventory along with inventory at the time of entering sales order as well as at the time of creating PO.  Thus there will always be a sub inventry associated with demand/supply.

Now business need to know the sub inventory associated supply/demands and how available qty is getting impacted due to same. In short business wants to see sub inventory value in the screen "Item Supply/Demand".

Any help how do I figure out the logic being data population on the screen "Item Supply/Demand".

Regards,

Vinod