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In Europe, the "." and "," characters in a number have the complete opposite meaning to when used in US/UK/Australian etc. numbers.

Not everywhere in Europe, it’s something country specific.

Also, a funny note: In Switzerland we have 3 formats depending if it is a currency, not a currency, or hand written :p

I would guess a comma.

That’s the locales for a bunch of countries:

> Argentina, Austria, Belgium (Dutch), Bosnia and Herzegovina, Brazil, Chile, Colombia, Costa Rica, Croatia,[44][45] Denmark, Germany, Greece, Indonesia, Italy, Netherlands, Romania, Slovenia, Spain,[46] Turkey, Vietnam.

Quoted from https://en.wikipedia.org/wiki/Decimal_separator

A comma.

Commas have been mentioned, also ' is used in some places.