Auto Generate PO from SO

SUGGESTED

Is there a catch to selecting the "Use Back Ordered Quantity" on the selection screen?  I would think this would populate the PO with the BO quantities on the SO correct?  I am populating the Back Order qty while the SO is still a Standard Order.  Another quirk I am noticing is when I try to group a few SO's together and the qty on hand is less than the ordered quantity the auto generation does not take into account of the quantities that are on previous orders.  My example is the INV7-4XL LON, the PO is calling to order 15 when it should only order 10, I have the option to order "Sales Order Qty" on?