Computer animation - 3D animation anyway - is usually not frame by frame animation. It's usually based on a set of key frames. These are major poses that the computer than creates steps between to create the final animation. If you have 10 major poses (aka key frames) all following one another directly (key frame on frames 1, 2,3,4,etc.)  and set your frames per a second to 30 you will have an animation that is less than a second long.  If you spread those key frames out so that key frame 1 is on frame 1 and key frame 10 is on frame 60 and play that at 30 fps, you'll create an animation that is 2 seconds long.

 

See the difference? Key frames are what you're animating. THAT'S what they have to do with frame rate. 

 

Edit: To summarize, How fast you get from point a to point b isn't just reliant on how fast you show the pictures but also on how many pictures you have to show.