How would I make a value like 03 using the variable value itself?

Does anyone know how I would make something like 03 using a 0, then the variable next to it? This is my current script

local timer = script.Parent
local minutes = 10
local seconds = 0
local milliseconds = 0

repeat
	if milliseconds < 9 then
		milliseconds = --What would go here, I can't do 0milliseconds or 0..milliseconds
		timer.Text = tostring(minutes)..":"..tostring(seconds).."."..tostring(milliseconds)
	elseif milliseconds <= 0 then
		seconds = seconds - 1
		milliseconds = 59
	end
until minutes <= 0 and seconds <= 0 and milliseconds <= 0