Why there is not any delay? I used wait(20)

uhhh another problem with the freezedown script. after the power out after 20 seconds it shut kill everyone. It works great but the wait(20) is not working it kills you rihght adter the power out

while true do
temp = game.Workspace.Temp.Value
if temp == -300 then
script.Parent.Parent.Ice:Play()
script.Parent.Parent.Music:Play()
script.Parent.Parent.Alarm2:Play()
wait(120)
script.Parent.Parent.Power:Play()
wait(0.1)
game.Lighting.Brightness = 0
game.Lighting.OutdoorAmbient = Color3.fromRGB(0, 0, 0)
wait(20) // here is the problem
for i, player in ipairs(game.Players:GetPlayers()) do
	if player.Character then
		local hum = player.Character:FindFirstChild('Humanoid')
		if hum then
			hum.Health = 0
		end	
end
end
elseif temp == -301 then
script.Parent.Parent.Ice:Play()
script.Parent.Parent.Music:Play()
script.Parent.Parent.Alarm2:Play()
wait(120)
script.Parent.Parent.Power:Play()
wait(0.1)
game.Lighting.Brightness = 0
game.Lighting.OutdoorAmbient = Color3.fromRGB(0, 0, 0)
wait(20) // here is it too
for i, player in ipairs(game.Players:GetPlayers()) do
	if player.Character then
		local hum = player.Character:FindFirstChild('Humanoid')
		if hum then
			hum.Health = 0
		end	
end
end
elseif temp == -302 then
script.Parent.Parent.No:Play()
elseif temp == -303 then
script.Parent.Parent.No:Play()
elseif temp == -304 then
script.Parent.Parent.No:Play()
else
script.Parent.Parent.No:Play()
end
wait()
end

Ok i solved it. I enabled team create .My really smart friend was editing the script and put a copy of it in workspace. The script killed everyone in 10 seconds.