This riffs drills the chromatic pentatonic í4/ë5 by starting melodic figures on that tone.
The workbook MS shows the riff played in G and A minors.
The on-page video also shows the study transposed into D and E minors – simpler because both are all-white-key. You should aim to be able to play this riff in C and F as well – that covers all the white-tonic pentatonic minors.
You could then play versions in C and D minors and in F and G minors.
Darting up and down the keyboard in both hands as in this study is a challenge in itself. Knowing just what you have to do and setting off in time is the secret.
If the movement really baffles you, move just one hand and play the other within a single octave.
Here’s a variation
that invented itself when Mister Musicarta took the advice above. It's in G and A minors.
Practising your pentatonic riffs will nearly always throw up variations, if you're listening out for them.