Hi sajid khan
1. April 2014 /3F1 = 780 then /3F6 was 780 * 12 = /3F6
2. April 2014 /3F1 = 600 (in case mid month joinee) then /3F6 was 600 + 780 * 11 (May to March) = /3F6
3. April 2014 /3F1 = 780 then /3F6 was 780 * 12 = /3F6
May 2014 /3F1 = 550 (in case of Loss of Pay) then /3F6 was April month 780 + may month 550 + 780 * 10 (June to March) = /3F6
Hope above calculation clear your doubts.