Pay Fixation from HONS to PG

I joined on 30.04 08 as an Asstt Teacher in Hons Scale ( Pre revised Basic Rs5500). According to Ropa 09 my scale was fixed in the New scale  ( Basic Rs 14930 ( B.P+GP)) and also my H.R.A was notionally fixed from Rs 825 to Rs 2240 though no cash benefit was given up to 31 st march 09 according to ropa. But now my scale Has been changed in M.Sc Scale with effect from 07.07.2008. ( Basic pay Rs 15960). and so on my admissible H.R.A. is Rs 2394 (15% of 15960) for the period of Aug 08 to march 09. My question is shall i get Rs 154/ month ( 2394 – 2240) in the period of Aug 08 to march 09 , and also Rs 123 ( for the period of 7.7.08 -31.07.08) as arrears

How did your basic pay changed from 14930 to 15960.? Please explain….