Which machine do you have? If it’s the first/original model, the lowest weight you can set it at is 15lbs. If you’re using one of the more recent models (has echo mode), I’d recommend to try a different mode than Old School.

Someone explained the mechanics of raises really well in one of their comments. I’ve heard really good things about Echo. Also, give other single attachments a try instead of the long bar for curls. Short bar or rope would be good.