When my battery is fully charged it says only 5-6 hours left should it no be 7?

Question

i got my macbook pro a few days a go and when my battery was fully charged it says ther is only 5-6 hours left , is there a problem with my battery

Answer 1

For starters, your battery will need to go through a few charge cycles before it reaches its full capacity.  That aside, most people won't hit 7 hours in normal use.  Apple (indeed, most computer manufacturers) tend to do their battery testing on very conservative settings (somewhat less than most people will use) so their reported battery run times are a "best case" scenario... not an average.
The time remaining indicator is also only an estimate based on your current usage.  Your battery has hardware internally that reports the actual percentage of your charge remaining.  Your computer than "estimates" how much longer the charge will last.  It works sort of like burning gas in a car.  The more processor intensive the task (i.e. pushing the gas pedal further), the shorter your charge will last (i.e. the faster you'll burn through your gas).
So, if your computer is just sitting there and you have absolutely nothing running and you have the display backlight turned way down, you may get an estimate of five or six hours... but if you start to watch a flash video or perform some processor intensive task, the estimated time remaining can change so something like three hours almost instantly.  It's basically calculating your remaining time on how you're using your computer "now" and that estimate will always update in real time based on your use.
If you want to get a better idea of how your battery is discharging, you can click on the battery icon and have the display show the percentage remaining vs. the time remaining.  When you display the percentage, you will get the actual percentage which will not fluctuate like the time remaining may.