Smelting

[Jamira33]

The furnaces consume nine pieces of (char) coal instead of eight for smelting a stack.

Formerly, it worked just fine with eight pieces of coal.
Now, the furnace starts burning the ninth piece of coal shortly before it is finished with the stack.

[ChrisKnight44]

I'm not entirely sure it's limited to a whole stack of 64 items.  I noticed a couple weeks back when I put 8 items in a furnace it would use two pieces of coal.  I figured it was just the tps being off a bit at the time and didn't think much about it.  Anyone know what could be causing this?