Right, I have encountered this a lot in my study and have used numbers like 0.0001 or even 0.000001 . I've managed fine using them but honestly have always wanted to ask this question but never got around to clarifying what I suspect. Right I think that the decimal in the first number I've mentioned is 1 thousandth and that the second number I've mentioned is ten thousandth (I think )

Before I started studying I'd only ever seen number after the decimal range from 0 to 99 and then if it reached more than 99 then the number before that decimal point increase by one.