Factorio Forums

Whenever I manually build one lamp, I have one copper cable and one iron stick left in my inventory. It looks like for each of those items, the last one is instantly crafted and goes into the inventory instead of being consumed.

The recipe need odd amounts but one starting product gives two intermediates, so you get the surplus.
NaB.

Yes, the lamp uses 3 iron sticks. 1 craft of iron sticks makes 2 sticks so you have 1 left over.

The lamp also uses 1 electronic circuit and 1 craft of an electronic circuit takes 3 copper cable. 1 craft of copper cable produces 2 copper cable so you have 1 left over after 2 crafts.