GetChildren not working as intended?

I have a :GetChildren() set up to detect if some text is equal to the amount of children, I am using a server script in server script service, I don't know what I'm doing wrong, I get no errors.

game.StarterGui.Game.Frame.Night.PlayersReady.Changed:Connect(function()
	local ign = game.ReplicatedStorage.InGameNames:GetChildren()

	if game.StarterGui.Game.Frame.Night.PlayersReady.Text == #ign then
		game.ReplicatedStorage.Values.DayNight.Value = true
	end
end)

You misunderstand StarterGui. Starter Gui is just the area that you put GUIs, in which them automatically get added to every played. I can see in the comments, you also tried game.Playergui, but again, you are misled.

The correct term for reaching a player's gui is game.Players.[Specificplayer].PlayerGui

to reach every player's gui, do the following

for i,v in pairs(game.Players:GetChildren()) do
	PlayerGui = v:GetFirstChild("PlayerGui")
	--Do whatever you want with the gui here--

Hope this solves your question, please comment if you have any queries or confusion. :)