How do make a GUI timer?

For a timer counting from 50 to 0. Here you go.

--Start counting.
for a=50,1,-1 do
--Some relayer here like gui.TextLabel.Text=a.." seconds left"
print(a)
wait(1)
end
--Some relayer here like gui.TextLabel.Text="0 seconds left"
print('0')
--What to do after timer hits.

a = 50
for i = 1, 50 do
wait(1) --How ever long, second minutes hours
a = a-1
script.Parent.TextLabel.Text = a
end

local x = 60
repeat
    wait(1)
    x = x - 1
    script.Parent.Text = x
until x == 0

Put this into a script. Put the script inside a TextBox/TextButton, and the timer should appear on the GUI.