With the Mazzer grinders, we generally don't rely on the numbers on the grind adjustment, and suggest using shot timing in order to get things dialed in. Ideally what you're looking for is 2 ounces of liquid to be extracted in 20-30 seconds for a double shot when you've tamped with 30 pounds of pressure. If nothing is coming out, increase the grind setting and then slowly dial the grind down as the machine is running.