R12: Encumbered Flag and Encumbered Amount Behaviour?

Hi All,I am trying to understand the behaviour of Encumbered Flag and Encumbered Amount Behaviour in Requisition , Purchasing and Invoices DistributionAfter doing a test in the system , i have observed that When a requisition is raised and not Approved  PO_Req_Distributions_All table has Encumbered Flag = Y  Encumbered Amount = Requisition Line ValueWhen a requisition is Approved  and PO is created PO_Req_Distributions_All table has Encumbered Flag = N  Encumbered Amount = 0.00PO_Distributions_All table has Encumbered Flag = Y  Encumbered Amount = Requisition Line ValueWhen the encumberance of PO is created the requisition's encumbrances are relieved, which is reflected in the Above encumbrance columns