Thanks for reply.
I gained awareness from a friend that this is something called Battery Calibration. When it showed me 55% initially, it might actually be very less and when it showed 100% in 2 hrs, it might be still very less in actual. I might have used all that very less charging and when switched off, it used up the left over even less battery.
I think if anyone else too faced this problem, it must only be in initial days. I am just hoping that i don't face this problem again.
Anyone body has any view over this, plz feel free to share.