Thanks for this…
There is only one way of writing musical notes - it includes the note, the length of the note and the way it should be played (soft, loud, staccato etc). The way it is written here does not follow this convention and is of no use for working out the timing. The bass notes as played by Justin are not all quarter notes (crotchets) - some are half notes (quavers). If a pattern is 1 2&3& 4 it’s 1 crotchet (a bass note), 4 quavers (bass note, treble note, base note, treble note) and 1 crotchet (the final bass note). If the pattern is 1 2 3&4 it’s 2 crotchets, 2 quavers and 1 crotchet.
As you say, the way to go is to play it using the timing in the video rather than looking at the notes here.
It made absolute sense as soon as I read your reply! I think I might be starting to get the hang of it!! Thank you to everyone who’s helped!!