“That can’t be right??” we hear you say :) It’s not, and it’ll soon be fixed. Let me explain why it happens. Today, savvy navvy assumes that you’re sailing the entire route. This means that if there are very light winds on that day (say, 2 knots) then if you were to try to sail you would move very (very!) slowly. At 0.0001 knots it would literally take you years to sail to your destination.
Very soon you’ll be able to set a minimum wind speed for when you usually switch on your engine to motor, and the speed you usually motor at. We will then account for this in the route which will make the estimated duration more realistic.