Garmin Personal Navigator GPS 100AVD Owner's Manual page 42

You may select one of four distance options:
· RNG -
· ATD -
· DMG-
· STR -
5-4
Range. RNG is the distance from your position to the "active
to" waypoint.
Along track distance. ATD is the along track distance to the
"active to" waypoint. It is measured from the point on the
course closest to your position.
Distance made good. DMG is the along track distance from
the "active from" waypoint. It is measured from the point
closest to your position.
Steer direction and distance. "L" indicates you should steer
to the left, "R" indicates you should steer to the right. The
distance indicates how far you are off course.