Maybe I can help you out.
First go back to the 8th notes and combine each group of 4 notes into a longer group of 8 and, for now, actually count the measure as 1 2 3 4 5 6 7 8.
This way the first group starts on beat one on the 5th fret of string 6 and fits exactly in one measure, the second group starts on the 5th fret on beat one on string 5 for a complete measure, then string 4, then string 3, then string 2. (You are playing an 8 note sequence starting from each string 6 5 4 3 2.)
But, when you get to string 2 in measure 5, you only have the first 4 notes of the pattern on beats 1&2! (I actually draw a line dividing the measure.) I call it the “turning point”, where you change from going up to going down. This is where you will mostly likely get confused in any of the exercises, so I always mark it.
So a new 8 note descending pattern starts in the middle of the measure on beats 3&4. As you descend you have a new 8 note pattern that always starts on the next lower string on beat 3 in the middle of a measure. You will end with only 4 notes starting from the 5th string.
Why all this bother?
Now look at the triplets.
The first measure has the same 8 note pattern and only half of the
next (=12 notes). So beats and measures are going to be at different places in the pattern when counting in 3's rather than when counting in 4's or 8's.
So, now think of measure 1 as a 12 note pattern played in 3s rather than 4’s.
Now each measure has a complete 12 note pattern rather than an 8 note pattern.
In 3 measures you play the entire ascending pattern of 36 notes (3x12). In 8th notes you played 4 and 1/2 measures which is also the same 36 notes (4 1/2 x 8).
But now the ascent ends at the end of a measure and the descent starts at the beginning of the next. The "turning point" is at the end of a measure. Three measures up and 3 measures down in 6 measures.
In 8th notes the turning point was in the middle of a measure and the complete pattern took 9 measures.
Now you start back down on beat one of measure 4.
This is the sticky part.
When you listen to Griff play triplets, you can easily hear the new 12 note sequence in 3’s going up, but as soon as he starts back down your ear shifts over to 4’s (or the 8 note pattern). (When you look at the slurs in Ex 27, they actually start out connected in 2's!).This also happened to me when I first started. It is very hard, at first, not to hear the 4 or 8 note pattern when coming back down.
I actually get lost if I try to count “correctly” i.e. 1 and a 2 and a, etc.
So I count simply 123,123,123,123.
My advice.
Treat it just as you would when learning a new solo, one measure at a time.
Without a metronome, as slowly as needed, practice only the descending pattern as follows:
Start with the triplets in measure 4 only. This is where you start back down (The "turning point").
1)Play the first 3 notes only. Count 1 2 3. Repeat. Repeat . Repeat....
2) Play the second tripllet only. Repeat.........
3) Do the same for the 3rd and 4th triplet.
4) Play the first 2 triplets, pausing in between. Repeat several times.
5) Play the first 3 triplets, pausing in between
6) Play the whole measure, pausing between the triplets.
7) Slowly play the whole measure without pauses, still counting 123, 123, etc
Once you get the feel for the new pattern you can practice counting "correctly".
Go through each of the remaining measures playing each triplet with a pause in between.
Practice each triplet and each measure slowly until you get a "feel" for it when you put it all together.
When you put it all thgether, you actually hear/feel a whole new “melody” coming back down than when going up.
That’s the whole idea behind “melodic sequences”. They aren’t meant to be used just as an exercise. Playing various scales using differnet sequences can open up new melodic ideas when soloing.