“Leave by” is the early edge of the window minus the door-to-aid time for that stop.

Before the start, times come from a pace model fit to TJ's Canyons 100 splits and run over this course's climbs and descents, scaled to a -hour finish.

Once he's moving, the tracker compares his actual time with that plan over the whole race and over his last 10 miles, and stretches or shrinks the rest of the plan to match. Early on it leans on the plan; by halfway it mostly follows what he's actually doing.

It also fits a trend line through his last 30 miles. If he's been steadily slowing (or speeding up), the estimate assumes most of that keeps going. The window runs from "the trend stops now" to "the trend continues in full", plus a margin, and it's wider on the late side.

His inReach sends a position about every 10 minutes, so the map lags a little. If the crew logs him in at an aid station, that overrides GPS.