One has five.
Two has two.
Three and four only have one.
What does eight have?
hints? who needs hints? :)
Updated hints from comments:
@ibrahim_mahrir - A hint? I'd suggest to contemplate What, when, where but not why? But that's as likely to be taken the wrong way as the right one....... :) Anyway, it's yours and mine, and a bit superficial too.
@Adam - the decrease isn't an essential feature [in the sense that, one having more doesn't of itself mean the next ones must have less]. I think that's a safe enough comment :)
Comments on the puzzle and its hints + answer (ignore this bit!)
I found myself looking at an ordinary analog clock on the wall, and thinking about how one never really saw the "1" in "10". You only tend to see ten as a unit, not it terms of its digits "one" and "zero". A bit like how the eye skips over the the typos in some sentences. The puzzle came full fledged from that. I wasn't sure anyone would get it, I wanted to find out if someone could, on such abstract wording.
I suspect my comment on the 7-seg guess was too cluey, but it really was inspired for closeness. Its hard to hint without narrowing it down. The hints above, well....
what/where/when - what are they and where/when are they [found], would be more productive than looking for a formula. Asking why are they, wouldn't help though. Mine+yours = ours ("hours"), and anything superficial is talking about things on the face of something (a clock face).