countdown clock

local timerLength = 120 --Time in seconds
local monitorLocation = "top" --The monitor location, it can be monitor_XXX or the side the monitor is on
local redstoneSide = "right" --What side of the computer the redstone is on
local redstoneSide2 = "left" --What side of the computer the redstone is on
local monitor = peripheral.wrap(monitorLocation) -- I get a handle for the monitor
function SecondsToClock(seconds)
  local seconds = tonumber(seconds)

  if seconds <= 0 then
    monitor.write("00:00");
  else
    mins = string.format("%u", math.floor(seconds/60));
    secs = string.format("%u", math.floor(seconds - mins *60));
    monitor.write(mins)
    monitor.write(":")
    monitor.write(secs)
  end
end
function ResetCountDown(number)
    sleep(number)
    monitor.clear()
    rs.setOutput(redstoneSide, false)
    rs.setOutput(redstoneSide2, false)
    os.reboot()
end
monitor.setTextColor(colors.orange)
monitor.setTextScale(4)
rs.setOutput(redstoneSide, false)
rs.setOutput(redstoneSide2, false) --put the redstone on
for i=timerLength, 0, -1 do -- we start the countdown loop
   monitor.setCursorPos(2, 1)
   monitor.clear()-- clear the monitor
   SecondsToClock(i)
   sleep(1) -- let a second pass
   if i == 20 then --check if we have reached 20
    monitor.clear()
    monitor.setCursorPos(1, 1)
    monitor.write("Ignition")
    rs.setOutput(redstoneSide, true) -- make it on
    rs.setOutput(redstoneSide2, true)
    sleep(1)
   end --close the if
monitor.clear()
monitor.setCursorPos(1, 1)
monitor.write("Liftoff")
end --we close the loop
sleep(timerLength)
ResetCountDown(10)