Description:

Coal / Charcoal should smelt 8.0 items, it actually seems to be smelting more like 7.9. The net effect is that if you balance your fuel and your smelt items, you always end up with one item left smelted.

Steps:

1. Put a 64 stack of cobble in the top of your furnace.
2. Put 8 pieces of coal / charcoal in as fuel
3. Wait till the furnace goes out.
4. Notice 63 items have been smelted instead of 64

Reproducable:

100%

Workarounds:

To workaround this issue, simply pay the stick-tax. Just put one stick in the fuel bin right before you put in your 8 pieces of coal, and all will work as expected.

Related issues:

Possibly related to MCPE-11268