> but I can say "there are 102 keys on this keyboard"

You can, but are there? Is the space bar grouped with them? You can decide either way, and either choice is defensible, so the count is dependant on our human categories.

Each key is unique, with the printed letter and with the precise arrangement of atoms differing. None of them are interchangeable. So you could decide that each key is in their own category. Or you could throw them in a bag with some dice and pebbles too and count the objects. Numbers are regarded as interchangeable, one "102" is the same as any other "102". Physical objects are not.

That's what I mean by saying that counting is an abstraction, and a number isn't a thing that exists in itself in the physical universe - it only occurs not "in itself", but once we can subjectively group things. There are "twelve keys" if you decide to group them as the same thing though they're actually not really. There's no physically existent "twelve".

I fully agree that "infinity" is a different kind of concept, less physically relatable even than "102". It's a further abstraction.