This exercise is an aggressive attacking exercise, for those who like to take advantage of the point early on in the rally starting with a flick. It is also a very good exercise for the controller as one of the hardest shots to play against is the flick/flat flick into the backhand corner as it forcers the controller to play the backhand with some topspin. For the exerciser, it is important to remember that when you flick the ball, there is almost zero chance that ball is coming back short, therefore take a big step out using your right leg (if right-handed, and use the left leg if you are left-handed).
This is a fantastic exercise to combat opponents who tend to play a lot of short receives from your service.
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.