Min Max Supply

What is considered as supply by the min max report?   I thought that supply was item quantities on approved requisitions or approved purchase orders.  However, we have an approved requisition that was autocreated onto a purchase order.  The PO was submitted for approval and rejected.  The requisiton was returned to the requisitioner, but then resumitted and approved.  The PO has been altered and is now In Process.  This quantity is no longer seen as supply by the min max report.  Is this how it should work?  Since there is still an approved requisition, it seems like supply should still be shown.