Aside from the obvious Jukebox thing, I can see this being used while ripping music from video games, where in some cases the tracks are only named numbers. I remember trying to rip the music from Mario Kart DS I think it was, and all the tracks were simply named SEQ_000, SEQ_001 etc.
In this case it wouldn't be appropriate, but "numero" does mean "issue" if you're talking about the issues of a magazine or comic book, etc (ie~ issue #4). If the hovertext is only intended to show the appropriate meanings for a given context, then it is wrong; however, if it is supposed to give all possible meanings, then it's correct.
NOMBRO VS NUMERO
Esperanto distinguishes between nombro and numero although both are translated as “number” in English.
Nombro is a number that signifies an amount or is used to express a mathematical relationship. For example:
la nombro de personoj
the number of people
4 estas pli granda nombro ol 3.
4 is a larger number than 3.
Numero is a number used for labelling items in a series:
la numero de la domo
the house number
la lasta numero de la gazeto
the last number [edition] of the newspaper.
Yes, the same in German: nombro=Zahl and numero=Nummer.
Before I started the Esperanto course, I never realised how often English uses one word where other European languages use two. Another example is 'to know' which can either mean scii (уметь?) or koni (знать?)
(I hope the Russian translations are correct. I do not speak Russian and had to copy and paste them from a dictionary.)
That would be an inquiry to the type of number it is (for example, a high number, a low number, a number that is a palyndrome when written down, ...) rather than precisely which number, so it would be a different question. In this context, "kiu" probably makes more sense, but I imagine there are situations thinkable where one would use "kia" to ask the other question.