Meaning of the Colored Arcs in the Tracks List

Two arcs are displayed for each track in the list. They denote the relative distance (orange) and duration (red) among all recordings of the same activity type. For instance, your longest hike’s ring(s) will be closed entirely, while a hike of half the distance (or duration, respectively) will display a semicircle.

The arcs are not related to the Activity Rings in the Activity app.