Second, your implicit premise is likely wrong. Different people have different talents and different challenges. Concrete example: In German we say eight-and-fighty for 58. Thus 32798 gets two-and-three-thirty-seven-hundred-eight-and-ninety where you constantly switch between higher and lower valued digits. There are many people, me included that not-seldomly produce "Zahlendreher" – transposed digits – because of that, when writing those numbers down from hearing alone, e.g. 32789. But then, there are also people for whom this is so much of a non-issue that when they dictate telephone numbers they read it in groups of two: 0172 346578 becomes zero-one-seven-two-four-and-thirty-five-and-sixty-eight-and-seventy. For me this is hell, because when I listen to these numbers I need to constantly switch them around in my head with active attention. Yet others don't even think about it and value the useful grouping it does. My current thesis is that it is because of a difference between auditory and visual perception. When they hear four-and-thirty they see 34 in their head, whereas I parse the auditory information purely auditory.
What I want you to take from my example, is that these issue might not be training problems alone. I have learned the German number spelling from birth and have worked in number intensive field and yet I continue to have these challenges. While I have not been deeply into history, I suspect that my troubles with Xth century versus x-hundreds might persist, or persist for a long time, even if I get more involved in the field.