This exercise uses the Dm7, Gm7 and Am7 chords which are each shown separately for you. Once you know how to play each chord try the exercises to get use to changing between chords and learning how to get the timing with your right hand by strumming as shown.
The Count 'numbers' show you the timing while the BLUE vertical
line (appears when you click on PLAY) shows you when to strum with your Right
Hand and how long to hold the chord with your Left Hand along with the count.