What is a number? That is a good question.
If you ask the somewhat educated layman, you might get answers such as "a representation of a physical quantity". You may get some other answers too.
But since mathematicians use words from natural language with a particular meaning, let's cut the foreplay, and skip right down to the mathematician part. However there is no agreed, or even common, definition for "number". The definition I have in mind, and I suspect that many mathematicians would agree with me, is the following one:
We say that $x$ is a number, if it is an element of a number system, which is a system representing and measuring a quantity of some form.
This definition allows for natural numbers, integers, rational numbers, real numbers, complex numbers, ordinals, cardinals, and so on. All these are number system. The only thing they have in common is that they measure some sort of quantity, and they represent it somehow.
Therefore, for me, the context "X numbers" means that "X" is some sort of form of measurement for mathematical objects.