How do I make a 30 Frames Per Second Cap?

I'm trying to run this script but it doesn't do anything? Does it have to be a localscript?

Here's what I have so far:

local RunService = game:GetService("RunService")
while RunService.RenderStepped:Wait() do
	local t0 = tick()
	RunService.Heartbeat:Wait()
	debug.profilebegin("30 FPS Cap")
	repeat until (t0+0.0325) < tick()
	debug.profileend()
end

Put this in a local script to cap the framerate to 30:

local RunService = game:GetService("RunService")

while RunService.RenderStepped:Wait() do
	local t0 = tick()
	RunService.Heartbeat:Wait()
	debug.profilebegin("30 FPS Cap")
	repeat until (t0+0.0325) < tick()
	debug.profileend()
end

You can't control the Roblox's client frame rate in a script.