In reply to David (in Normandy) )
who wrote this in , I, Marvo, say :

I do recall thinking that their numbering system of
septante and nonante for seventy and ninety was a great deal more
'sensible'
than that of the French!
Sacha

I'm still learning the language and am just about there with the
numbers now. A few months ago I made quite a blunder in the local
bricolage store though. I'd stacked 16 fencing stakes on my trolley
and the lady on the checkout asked me how many I'd got. My mind went
blank, then I thought 17 is dix-sept and 18 is dix-huit so therefore
16 must be dix-six. So I said "J'ai dix-six" - and got the most
peculiar look back. She repeated the question and I pointed at the
stakes and repeated "J'ai dix-six" and I got another weird look, so
she got out of her chair came round and counted them herself then
exclaimed "Ah! Seize!". It wasn't until I got home that I twigged why
I got such a strange look - when she asked me how many, I was in
effect saying "They are dead!".

Worse is Swiss French. They have words for seventy and ninety as well ...
septante and nonante (IIRC).