Sometimes, computing the shortest route might not be the best idea. In some buildings, computing the shortest route might be at the expense of requiring that the user performs unnatural floor changes. 

Consider the following example. The user is at point S (Start) and wants to go to point E (End). Due to the atipical morphology of the Level 1, the shortest route requires the user to move up to Level 2, traverse it, and go back down to Level 1.  This is clearly unnatural and probably a waste of time. A more natural way would be to go up from Level 0 directly to Level 1, even if this implies walking a longer distance.

If your building, due to its morphology, presents such situations, you may try to turn ON the "Minimize floor changes" option in the Route and Navigation Settings.