dim up / down to percentage

[KoBra]

I run this script to change up/down dim to a percentage but when it runs the logic machine goes in overload (100%) Is there another/better way?

Code:

dimmer = grp.getvalue('1/3/10')
step = bit.band(dimmer, 0x07)

if step ~= 0 then
  addr = '1/4/10'
  up = bit.band(dimmer, 0x08) ~= 0
  value = grp.getvalue(addr)

  if up then
    newvalue = value + 5
  else
    newvalue = value - 5
  end

  -- clamp between 0 and 100
  newvalue = math.min(newvalue, 100)
  newvalue = math.max(newvalue, 0)

  if newvalue ~= value then
    grp.write(addr, newvalue)
  end
end

os.sleep(0.2)