How could i fix/do this?

For one it does not count down properly, and two, how could i make it so it works correctly? Is their anything wrong with this? Its a round countdown, i just want it more fancy and advanced.

local Second = 60
local Minute = 05
local Minutes = "0"
local Seconds = "0"

while true do
	wait(1)	
	if tonumber(Second) < 60 then
	Second = Second - 1	
	if tonumber(Second) == 00 then
	Minute = Minute - 1	
	end
	end
	if tonumber(Minute) < 10 then
		Minutes = "0"..Minute
	else
		Minutes = Minute
	end
	if tonumber(Second) < 10 then
		Seconds = "0"..Second
	else
		Seconds = Second
	end
	script.Parent.Value = "Time left: "..Minutes..":"..Seconds
end