Many countries, eg England, use Decimal = ‘.‘ and List Separator = ‘,‘ ie (1.2, 3.4)
Others, eg France, use Decimal = ‘,‘ and List Separator = ‘;‘ ie (1,2; 3,4)
The computer must use the same for ALL applications so that, for example, both Excel and Autograph are expecting the same convention. Additionally Autograph uses the List Separator to enter Parametric Equations, eg x = sint, y = cost.
Apple and Windows computers treat this topic a little differently.
Download this Word doc that summarises the situation: