When creating a route, the elevation loss and gain are reported differently when editing than after the route is saved. This is due to how the information for the path the route follows is processed after being saved.
Many users report that the elevation stats after saving are higher than expected by between 10-30%. You may find that the more accurate ascent and descent stat can be viewed in edit mode.
We're are continuing to monitor this issue and evaluating what the best potential fix might be.