That’s if you have 100% accuracy. In practice it’s always more. For instance, I have about 90% accuracy across the levels (a bit less in A1), and that gives me 10.15 reviews per lesson. The difference might not seem big, but multiplied by your lesson rate, that can end up being many more minutes per day.
Source: Choosing the right pace for your lessons (thanks to queueing theory) - #34 by Tenoch