In the image below you can see that it says “10 of 9” and that is one extra compared to the max capacity:
It may be causes from one player leaving and one joining so fast that the server is unable to remove the old player from the count fast enough.
Expected behavior
It should say “9 of 9” and not anything more
This is a very old “bug”. Previously, it could be implemented if several players joined in at the same time (on an almost full server). Now I don’t know if this method works.
This is easily preventable… whoever works for Roblox and forgot to check for this should be investigated by the leaders of Roblox Staff. If they can’t even prevent something as simple as this… what’s to say they aren’t behind other issues on Roblox? Anyways here’s the fix
local Players = game:GetService("Players")
local MaximumPlayers = Players.MaxPlayers
while true do
task.wait(1)
local currentPlayers = Players:GetPlayers()
local numberOfPlayers = #currentPlayers
if numberOfPlayers > MaximumPlayers then
local randomIndex = math.random(1, numberOfPlayers)
local playerToKick = currentPlayers[randomIndex]
if playerToKick then
playerToKick:Kick()
end
end
end
Never do that, it create a instant and useless loop and kick a player that was totally innocent. Use this instead!
local MaxPlayers = game.Players.MaxPlayers
game.Players.PlayerAdded:Connect(function(player)
if #game.Players:GetPlayers() > MaxPlayers then
player:Kick()
end
end)
I don’t think it’s because there is more people in server. I think it may be a visual glitch from very busy servers. I tried joining one of these overflowing servers and the server is very busy 
I doubt this is a actual extra player in the server. But regardless, visual glitches and possibility serious glitches like these should be fixed for stability. I heard they are going to make their servers very fast in future, but if they wanna do that they should fix all the glitches to prevent unpredictability.
Edit: I just realized
Servers that have no one in line have the correct “9 of 9” text
However servers that have more than 1 person in line has the “10 of 9” player
This still should be fixed as “10 of 9” only confuses people
I thought about it and you are right to try that and see if it would help. It does at least add an additional verification unlike currently where internally it possibly doesn’t add any whatsoever. However it’s not guaranteed to work. It would have to be heavily experimented with and honestly most people don’t have the time for that. At least with some kind of loop even if a player added fails for whatever reason it forces the game to fix it. I would trust child added in the players service more than I would trust player added but that’s just me knowing the possibility that they could already have what you’ve shown set up internally and it fails anyway.
