im in the same boat at you mate, im running my MBP on its first full charge and as soon as i turned it on after a whole night charging it went straight from 100% to 99%
It said I had 10.28hr battery when first switched on but 15 mins later its dropped to 95% and got 6 hours battery
I think it needs a couple proper charges for it to learn
Also how bright is your screen and what are your battery settings? mine screens down a few clicks and on energy saving settings