D, U, K - down, up, skip, step
All those little notations indicate that this is an invitation to look closely at the PATTERN!
D is for down, U is for up - from the note, not to it.
The first six notes indicate the pattern for the following groups of six, until you get something new - the last three notes in this case.
Coming down shows a 'k' - for skip. We're dealing with the E minor pentatonic scale - shown at the start of the line, followed by (0), which indicates there are no black keys in the basic E minor pentatonic scale - so the skip is from the tonic to the fifth (e to b).
If you don't see a 'k' for skip, it's 's' for step, which is the default so doesn't need indicating.
The T, 3, 4, 5 etc in between the staves are the on-the-beat RH notes. The same notation under the music is for the LH notes. (The 'R' should be 'T' for tonic...).
You'll notice in fact both hands essentially play straight up and down the minor pentatonic scale, but the right hand with decoration.
The pattern modulates up a semitone, but to do that the right hand falls a major third (M3), and the left hand a whole-tone (w-t).
Overall, the exercise rises a fourth, from E to A, by semitones. This is the best section of the octave to play this exercise on.
So, there are two ways to think about this exercise.
- An exercise in 'getting the pattern'. Scale patterns - both diatonic and pentatonic - generate music for free; spotting and following them is a key musical skill.
- After that, an exercise in finger dexterity and adapting the fingering to the unique black/white-key combination to the new key.
A useful challenge all round!