The handwriting of numbers and letters being confusing between countries is something that's easy to not think about until you've actually faced the issue multiple times.

I'm English, and I can't honestly remember which country it was that I've lived in (I think France...) where there were a couple of numbers that even after living there for a year I still wasn't confident reading when hand-written on things like café menus. And I don't think I would have thought of that being a systemic issue rather than just blaming an individual's handwriting before I lived there, despite having taken over 100 trips to France before moving to live there for a year.