Using coals doesn't smelt the same amount of items as previous version

Summary
When you smelt anything using coals, using one coal only gives you 7 smelted item instead of 8.

Step to Reproduce
1. Smelt/cook any item (8 items) inside a furnace/blast furnace/smoker with a coal.
---> Only 7/8 are smelted/cooked.

Original Description
Smelting cobblestone, stone, sand etc with 8 coal only smelts 63 instead of 64.