Putting wood stack in furnace leaves wood behind/generates wood

I made a video for you to make it clear.

If I put a 2k stack of wood in the furnace 4 wood will be left in the inventory though the whole stack had been transfered.

Just realized the 4 wood are not being generated, they come from the another stack in the inventory. But why does it do that?

Hello???

I cant see the video. can you repost it

Wasnt a video. It was a pic.

Here you can see the wood is still burning even though no more ore can be melted due to the full output.

Wrong thread!

I dont have the video anymore.

This was last October.