Actual fuel consumption differs from recipe values.

For some reason, the fuel consumed when running a factory is not the same number as state in the recipe. The factory will complain it does not have enough fuel, but will finish its cycle anyway.

For example, the _Smelt Stone_ recipe of the _Basic Contraption_ claims to require 10 coal, but actually only consumes 6, leaving the remaining 4 in the furnace.
