Tension settings have always stumped me. I always just leave the tension on whatever the serviceman does. My Janome has an "auto" setting which I usually use, but occasionally I need to change it because of the seam drawing up a bit. Not sure why it does that but what I do usually works. I think different threads has a lot to do with it. I've only been sewing 63 years and am still in the dark about some things.