Windows Furnaces counting as two machines in the "Machines Ready:" tab on the Farm Computer

[LIONFORCESXV]

I find myself confused since today i saw that a furnace that had finished smelting a gold bar counted as two machines on the farm computer (it stated "Machines Ready: 2" but when i collected the gold bar it went back to "Machines Ready: 0"). Anyone else finding this? Is it a bug?