Oh sorry, I confused that tutorial with one on my Moving With Motion training DVD. The Look-ahead frames feature is a way to give Motion a hint. If you have a fast-moving object or a object moving in a straight line...with nothing in the way. It lets you look and then track frames ahead of or behind the playhead (behind if the reverse checkbox is checked). I hope this helps. Here is instructions on how to use it:
To define look-ahead frames
1-Apply an Analyze Motion behavior to a clip.
2-In the Canvas, position the tracker on the desired reference pattern.
3-In the Behaviors tab of the Inspector, use the Look Ahead Frames slider or value slider to specify how many frames you want the tracker to look ahead.
Note: The maximum default for the Look Ahead Frames slider is 10 frames. However, you can enter a larger frame amount using the adjacent value slider.
3-While holding down the Command key, click the tracker in the Canvas, then drag in the direction the reference pattern is moving in the clip.
As you Command-drag the track point, an inset displays a magnified view of the frame specified in the Look Ahead Frames parameter.
4-When the look-ahead tracker is positioned on the reference pattern, release the mouse button.
When you click the Analyze button, the new reference point is used as the tracking pattern.