A few thoughts:
1. Batteries don't all have the exact same capacity...yours may be just under normal full capacity.
2. Batteries lose capacity over time. How old is your computer?
3. Did you calibrate your battery? Instructions are in the manual. You should do this every month or two.
4. If you plug in the computer and the battery is at 93% or greater, it won't charge the battery. This helps prevent overcharging and brief charge/discharge cycles that tax your battery.