Recently got a Santoker WS-3 from China and I don't think the instruction manual is clear enough as it's translated from Chinese. I need some help setting up airflow with the machine. The variable speed chaff fan is the main fan for airflow. The manual said to set airflow at 40% at the start of the roast but there's no indication of what speed to set the chaff fan at. At what speed do I set the chaff fan?