This exercise is a good warm-up exercise to improve movement and improve the forehand topspin and backhand topspin. Movement in this exercise can prove difficult if the controller aims to achieve good angles. It would be good practice to play one topspin on each side with heavier spin, and one topspin on each side with more speed. This will allow you to improve the adjustments required between the two types of shots.
Though TTFit set out exercises for you to try, they are mostly there for inspiration - feel free to deviate and adjust to suit your game better. The most important this is that you give it your best... always.