So a campfire. Early days it's the only way to cook food. My personal take is that FC is making his thoughts known to us, who must count every sawdust, and just saying, "Really. Get a life. In the end a few extra sawdust won't matter." That said I think BTW trains us, sometimes strictly, that EVERYTHING matters. So...
A campfire holds 10 sawdust. Sticks are worth two sawdust. Bark and saplings worth one.
Two food can be cooked in a night. Light the fire, use 4 sawdust, then 10. Swap the food. Then 10 and finally 4. (4-10-10-4).
So the math is simple. Unless you pay attention. Food is either 20/14 sawdust (the campfire itself is worth 6) or 17/17 sawdust. So yeah, a few extra sawdust won't matter but here are the numbers if you want to keep it tight.