Live Chess has three different ratings based on different time controls:

• Bullet rating - For games under 3 minutes.
• Blitz rating - For games of 3 minutes to 14 minutes.
• Rapid rating - For games 15 minutes and longer.

We keep these rating separate because of the largely different skills involved in playing shorter or longer games. 

Note that the per-move bonus time is significant - not just the base minutes. 

The system assumes an average game-length of 40 moves to estimate the total length of time available to each player; the result is what determines which rating is affected by a given time control:

A time control of 2 | 12 therefore results in a Blitz (not Bullet) game like so:

2 minutes + (12 seconds x 40 moves = 480 seconds) = 10 minutes

As a reference, here are some examples of presets available in Live: