Stand on the actual line when you set it, in open sky if possible. The timer starts when you walk out of the start zone. Each time you pass back through the zone counts one lap, and the walk finishes automatically on the final lap (e.g. 5 laps of the 400m route for 2km).
Timer starts automatically when you leave the start zone.
Keep this screen on — do not lock your phone.
Tip: open this page in Safari or Chrome itself (or add it to your Home Screen) — links opened inside another app can auto-lock the screen.