We're talking about file systems.

Then where are we getting 5 billion? The most common filesystem limits listed seem to be 2^32, which is a touch over 4 billion, and 2^64, which is Big.

(i.e. I can see now what I think you meant, but "5 billion" is a much closer match to "5 million" than 2^32)

My brain doesn't do numbers so good, so 4,294,967,295 became 4,924,967,295 and I rounded up instead of down.

Ah, that makes sense. Completely understandable:)