The numbers DO matter, that's how they denote their ranking. Both the Lower and Upper Moons are ranked from 1-6 with 6 being the weakest and 1 being the strongest. For example, Lower Moon 6 is technically ranked 12th out of the Kizuki and Upper Moon 1 is ranked as 1 overall
Polygon
2019-10-03 14:33:20 +0000 UTC
I haven't read the manga but i know there is the lower moons and the upper moons. The lower moons are extremely weaker than the upper moons. There is such a difference in strenght you can't even understand how they are in the same group. Now i don't know exactly know if the numbers say anything but it shouldn't matter to much.