In my case, because callisto is not supported yet, I had to set another coin for the dev fee due to having a graphic card with low memory (dag size). I chose pgc because I assumed that it was going to have a smaller dag than ETH (the default one).
If you are mining etc by all means set it at etc so it doesnt have to download the dag from a different coin and it will use the same one you loaded when you started the miner.