@Mosimann if you have any "Skip/Offroad" segments enabled on any of the waypoints included in the route then this will throw off the total mileage & make the mileage at later waypoints incorrect
You could also try using a different routing calculator, from memory I think there may be an issue with Here & ferries with the pdf output, I believe it should be correct with the OSM calculator
Hopeful this issue is resolved/not in the new planner