count | no_of_mon | total
-------+-----------+-------
     2 |         6 |  1577
     9 |         7 |  1570
    11 |         8 |  1568
    12 |         9 |  1567
    17 |        10 |  1562
    31 |        11 |  1548
    44 |        12 |  1535
  1162 |        13 |   417
   291 |        14 |  1288


here the total of column count = 1579 (2+9+11+12+17+31+44+1162+291)

the way i need to fill the column total is

total 
1577 (1579-2)
1568 (1577-9)
1557 (1568-11)

. 
.
.
.
.

pls tell me how to do that