For others who don't know, for me (American), a period means a decimal value and a comma separates between thousands. I think in some parts of Europe it's the opposite, where the period separates thousands and the comma means a decimal value.
... this is the one difference between EU and US numbering and units where EU is just wrong. :-)
Edit: I see below the Swedes are even more wrong. Bork bork bork!
I've heard that, but I think it's trying to back into a rationale since it makes no sense, people do multiply by 3 digit numbers.
FWIW, when I was in grade school in France, no, we didn't separate thousands by space. Then again, my school was on the border with Switzerland, so *shrug* who knows!?!
[1] https://learn.microsoft.com/en-us/globalization/locale/numbe...