Imagine a bridge that's 100 ft long. Now let's say this bridge could be made to be any length long you're willing to dream of. However if you look at this bridge, regardless of how long it could be, it's right now it's only 100 ft long. This is what I mean by unlimited - to not posess a limit to how long the bridge can be, though the bridge is just some finite length long. An infinite bridge on the other hand has actually be infinitely long, which is what makes no sense.
Something is only infinite if it "completely fills" the entirety of all it's unlimited potential, but you can't actually do that, so nothing can be infinite. Every thing in this world is entirely limited.