I don't know exactly what media format your camera produces. I assume when you ask how to remove the "extra frames" you are asking about how to remove pull down.
Go into your help file and look up "Remove 3:2 or 24Pa pulldown from video" you can learn more about this.
In the Project panel, select the footage item from which to remove 3:2 pulldown.
Choose File > Interpret Footage > Main.
In the Fields and Pulldown section, select Upper Field First or Lower Field First from the Separate Fields menu.
Do one of the following and click OK:
If you know the phase of the 3:2 or 24Pa pulldown, choose it from the Remove Pulldown menu.
To have After Effects determine the correct settings, click Guess 3:2 Pulldown or Guess 24Pa Pulldown.