Estimates are based on distance and elevation using your Hike Time settings, which default to 5 km/h (3.1 mph) walking speed and 600 m of ascent per hour. Change them at Home > Settings > App Settings > Customise > Hike time settings — pick a preset or set a custom pace (you can also reach this from the map options while navigating). The pace setting goes up to 10 km/h; estimates are designed for hiking (there’s no cycling mode) and factor climbs but not steep descents yet.