I also forgot that the Multi-Moons do count as 3. They only take up one spot in the list, but it shows the number next to it. That may be why some people are getting different numbers. I counted the amount of moons in the lists for each Kingdom, and only came up with 836,
not including multi-moons (e.g. Multi-moons are counted as 1)
Since I haven't obtained all the listed moons, I can't tell which ones may be multi-moons, so I can't count the total of moons they give you, but I'm gonna guess it brings that total up to 880. The only problem is, there is an odd moon amount. The difference between 880 and 836 is 44. 44 is not evenly divisible by 3, so yeah, I dunno. There are not 14.66666666666667 Multi-moons, that's for sure
In-game listed totals for each Kingdom:
Cap 31
Cascade 40
Sand 89
Lake 42
Wood 76
Cloud 9
Lost 35
Metro 81
Sunshine 71
Snow 55
Luncheon 68
Ruined 10
Bowser 62
Moon 1 38
Mushroom 104
Moon 2 24
Moon 3 1