In Sumerian (and thus Akkadian, Hittite, etc) cuneiform, there are often several glyphs which have the same pronunciation (as far as we can tell). So the glyphs pronounced
/u/ will be transliterated as U/U₁, Ú/U₂, Ù/U₃, U₄, U₅, and so on.
But how are these numbers assigned? Why is 𒌋 U₁ and 𒌑 U₂ rather than the other way around, for instance?