Weird double counting of inventory. [solved]

local chest=peripheral.wrap("back")
local count=0
local list={}
--print(chest.listMethods())
for c= 1,27 do
  if chest.getStackInSlot(c) then
    for i,v in pairs(chest.getStackInSlot(c)) do
      list[i]=v
    end
    if list["display_name"]=="Iron Ingot" then
      count=count+tonumber(list["qty"])
      print(list["qty"])
    end
  end
end
print("payment detected: "..count)