local sensor = peripheral.wrap("right")
local targets = sensor.getTargets()
local totalStackSize = 0
local currentStackSize = 0;
local percentage = 100;
while true do
  local details = sensor.getTargetDetails("bottom")

  local firstSlot = details[1];
  currentStackSize = tonumber(firstSlot["size"])

  -- the stack size has increased, so we've probably added to the machine
  if currentStackSize > totalStackSize then
        totalStackSize = currentStackSize
  end

  percentage = (100 - ((100/totalStackSize) * currentStackSize));
  print( percentage.. "% of the way through")

  sleep(0.5)
end