I've been spinning regularly and it is true. You work as hard as you can. Your instructor will tell you "turn your knob up a 1/4 turn" or "let's bring this up to a 7/10!" or something like that. As for the first, who is going to know if you don't turn it a 1/4 turn? As for the second, the 10 scale is the maximum effort you can put in while dying and so a 7 would be up to how you feel. And it usually changes within weeks... you'll be able to do more quickly. Within a month of spinning a felt a huge difference in the way I rode my bike. I was a lot more stable and my form was way better. I highly recommend it!