^^Battery back-up would vary depending upon the load,power mode and brightness settings.
It is normal.While gaming the battery back-up would go down at a higher rate.
Preferably while playing games keep the laptop in AC mode rather than battery mode.
On normal usage you should be able to get more battery back-up.
Well,only way to confirm if your laptop is full charged is by logging in to your OS.
In this laptop when the battery is being charged and the battery is charged between 20-80% the battery indicator would be blinking white,it would blink in every ~5seconds.
When it is being charged and the remaining charge is more than 80% then it would emit a steady white colour.
If you are thinking about overcharging of battery if it is kept under AC mode for long duration then don't worry,it won't happen.
Only way the battery can be overcharged is if the charging system malfunctions and then the battery overheats due to this while in the charger.