I have to admit, as a French myself I found relief in that discovery. And thank you very much for the explanation.

I was confused by the "2 and" at first, then I realize you put the smallest part of the whole number first. It makes perfectly sense if you count in base 20.

We also have an habit to count in base 12 and half 12 in France. Like "half a dozen" (6) or "one dozen and half" (18), but only for multiple of 6.

I will now say "quatre vingtaine et demie" instead of "quatre-vingt-dix" just to tease my fellow Belgians (who say "nonante" and "septante" instead of "soixante-dix" et "quatre-vingt-dix")

EDIT: As a matter of fact, I will rather say "trois et demi-cinquième vingt" for 73 because it sounds better. Now I see it.

If I am correct, the 3rd 20 is everything between 60 and 79. The half-3rd 20 is everything between 70 and 79. So 7 and half-2nd 20 would be 37?

How would you say 40, 60 and 80 then ? 2nd 20, 3rd 20 and 4th 20?