What does the bonus time mean; how is it figured?  How is this bonus enabled?

The bonus time is time added to your time after you make each move.

Thanks; for instance?

You will see time set like 15-0 meaning its a 15 minute game, if you see like 10-10 or 15-15, it a fifteen minute game with 15 minutes bonus time.  Once you make a move some time is added to you game.  It makes it a 30 minute maximum if it adds it all.   The computer figures and adds it.  I really dont know how it does it...

This helped me understand quite a bit: http://blog.chess.com/DrawMaster/how-to-calculate-the-effect-of-bonus-time

5-2 means for every single move,you get a addition of 2 seconds extra