General Purpose Countdown Timer with monitor support

print("")
term.write("Enter hours: ")
local nHours = tonumber(read())
nHours = nHours or 0
print("")
term.write("Enter minutes: ")
local nMinutes = tonumber(read())
nMinutes = nMinutes or 0
print("")
term.write("Enter seconds: ")
local nSeconds = tonumber(read())
nSeconds = nSeconds or 0
term.clear()

local totalTime = (nHours * 36000) + (nMinutes * 600) + (nSeconds * 10)
if totalTime == 0 then print("") error("No time to count down\n", 0) end
local hours, minutes, seconds, sHours, sMinutes, sSeconds, sTenths, countdownTimer, timer, _
local mon = { peripheral.find("monitor") }

if mon then
  local x
  for i = 1, #mon do
    mon[i].setTextColor(colors.white)
    mon[i].setBackgroundColor(colors.black)
    mon[i].clear()
    mon[i].setTextScale(1)
    x = mon[i].getSize()
    if x == 7 then      --# width = 1
      mon[i].setTextScale(0.5)
    elseif x == 18 then --# width = 2
      mon[i].setTextScale(nHours < 10 and 2 or 1)
    elseif x == 29 then --# width = 3
      mon[i].setTextScale(3)
    elseif x == 39 then --# width = 4
      mon[i].setTextScale(4)
    elseif x >= 50 then --# width = 5+
      mon[i].setTextScale(5)
    end
  end
end

for i = totalTime, 0, -1 do
  hours = totalTime > 35999 and math.floor(totalTime / 36000) or 0
  sHours = tostring(hours)
  minutes = totalTime > 599 and math.floor((totalTime - (hours * 36000)) / 600) or 0
  sMinutes = minutes > 9 and tostring(minutes) or "0" .. tostring(minutes)
  seconds = totalTime > 9 and math.floor((totalTime - ((hours * 36000) + (minutes * 600))) / 10) or 0
  sSeconds = seconds > 9 and tostring(seconds) or "0" .. tostring(seconds)
  sTenths = tostring(math.floor(totalTime - ((hours * 36000) + (minutes * 600) + (seconds * 10))))
  term.setCursorPos(1, 1)
  if totalTime == 0 and term.isColor() then term.setTextColor(colors.red) end
  term.write(sHours .. ":" .. sMinutes .. ":" .. sSeconds .. ":" .. sTenths .. " ")
  if mon then
    for i = 1, #mon do
      mon[i].setCursorPos(1, 1)
      if totalTime == 0 and mon[i].isColor() then mon[i].setTextColor(colors.red) end
      mon[i].write(sHours .. ":" .. sMinutes .. ":" .. sSeconds .. ":" .. sTenths .. " ")
    end
  end
  if totalTime > 0 then
    countdownTimer = os.startTimer(0.1)
    repeat
      _, timer = os.pullEvent("timer")
      if timer == countdownTimer then
        totalTime = totalTime - 1
      end
    until timer == countdownTimer
  end
end
print("")