The suffix "-s" is used to indicate plurals, which, in English as well as many other languages, is simply any number aside from one. In other words, plural just means a count isn't singular.
For example;
One mile - 1 is equal to 1, singular.
Zero point one miles - 0.1 is not equal to 1, plural.
Two miles - 2 is not equal to 1, plural.