The decimal point and comma 

The U.K and the United States are two of the few countries left in the world that put commas and decimal points in a different place in a series of numbers, for example:

UK/USA = 3,943,627.374

Spain = 3.943.627,374

Also:

UK/USA = 24.8%

Spain = 24,8%

So to remember this, just recall that whatever the U.K or the U.S.A does, Spain does the opposite or the other way around.