It might seem like an oversight, but the lack of lines and numbers is intentional. The short answer is that your roast set to "2" for 7 minutes is not like Joe's across town or Julie who lives in a 1930s apartment or Jack who roast outdoors in the Colorado winter. Line voltage, voltage drop, environmental temperature - this and other factors makes one roaster different than another, even when all the heat dials are set to 2 or C or Medium. What I like to do is make my own marks on the heat knob for settings that work for me. We also include a sort of "template" in the printed material with Popper you could use to add a scale to the knob, if you want to. Anyway, there's way more to say on this, but we thought it best that YOU create marks on YOUR roaster so they actually mean something to YOU! That is, if you really want marks. I'll going deep into this in a separate post.