I sometimes see this, too.
In my country (UK),we drive on the left but I also drive a lot on the Continent, where they drive on the right. I see the misnumbering here at home and abroad, so it has nothing to do with the side of the road you drive on.
What I think is happening is that MyRoute sometimes interprets a small side road ‘exit’ (sometimes leading nowhere other than to a gated field or a tiny road, used only by a person on foot or now just redundant) as a full exit, whereas other apps ignore it.
I have seen other apps do the same thing (ie. adding an extra ‘exit’) when MyRoute ignores them.
I have also seen some apps interpreting large roads, where there is an exit lane off the roundabout and an entry lane onto the roundabout, as both being exits.
Sometimes, you just have to use your common sense and ignore the number.
PS Most roundabouts have a sign on their approach, showing where the exit roads lead to and their position on the roundabout. Use the information the signs give, alongside the navigation, to help work out which exit to take. Just like we used to do before navigation app’s appeared to rule our lives.