Garmin GPS IIplus Owner's Manual page 76

Reference
Fig. 70a
Fig. 70b
70
Track Log Display
The track log option sets the number of points the unit will attempt to display
on the Map Page. The default setting of 250 points provides good resolution with
minimal screen clutter. The maximum setting is 1024 points. Once you've reached
the maximum number of track points, the older points will be lost as new points are
added. Note that adjusting the track points displayed will not affect whether the
receiver records a track log or the ability to create a TracBack route.
Managing and Clearing the Track Log
The rest of the track setup window displays the percentage of available memory
currently used to store track log data, as well as function fields to clear the track log
memory and activate the TracBack feature.
To clear the track log:
1. Highlight 'CLEAR LOG?' (Fig. 70a), and press ENTER.
2. Highlight 'Yes?' (Fig. 70b), and press ENTER.
Note: It' s a good idea to clear the track log at the end of the trail head, etc., in
order to make the best use of the TracBack feature.