I have created a query to get actual,budget,encumbrance amount.but encumbrance amount is coming wron

HI,

I have created a query to get actual,budget,encumbrance amount.but encumbrance amount is coming wrong,even with the same query actual and budget amounts are coming fine,query pfb

SELECT concatenated_segments, period_name, budget, encumbrance, actual,

       (nvl(budget,0) - nvl(encumbrance,0) - nvl(actual,0)) available

  FROM (SELECT   gck.concatenated_segments, b.period_name,

                 TO_NUMBER

                        (NVL (SUM (DECODE (b.actual_flag,

                                           'B', (  NVL (b.begin_balance_dr, 0)

                                                 - NVL (b.begin_balance_cr, 0)

                                                 + (  NVL (b.period_net_dr, 0)

                                                    - NVL (b.period_net_cr, 0)

                                                   )

                                            )

                                          )

                                  ),

                              0

                             )

                        ) budget,

                 TO_NUMBER

                    (NVL (SUM (DECODE (b.actual_flag,

                                       'E', (  NVL (b.begin_balance_dr, 0)