Apply your scale knowledge on the neck and play any Major Scale on the guitar using only one string!
View the full lesson at One String Major Scales | JustinGuitar
I’m confused. At the beginning when you go tone tone semi tone, you jump 2 frets for the semi tone.
Thomas welcome
Each fret is one semintone apart, not two.
So from the open E string the first fret is F, as E and F are a semitone apart. From F you go up two frets to the third fret to find G. F and G are a tone apart. A is on the 5th fret B on the 7th C on the 8th, B and C are only one semitone apart the same as E and F. Another two frets to rhe 10th D, then two frets to E on the 12th. Then start again.
Hope that helps.
Hello and welcome.
I think you need to have a closer look at the video, but yes even though I already knew the formula it didn’t come across the way it should when I first watched it. Sometimes Justin says the step before he does it, sometimes while he’s doing it. This is an exercise where it is easier to do it for yourself rather than follow along with the video. The text is super explanitory so you can’t go wrong.
Hello @tml6866 and welcome to the Community.
As others have said, one fret = a semitone always.
It may be that Justin’s words are slightly out of sync with his fingers on any given movement but if you track all his movements with all his words they match.
Hope that helps.
Cheers 
| Richard_close2u | JustinGuitar Official Guide
I remember one string major scales as if it were a phone number. 221-2221. It’s an easy to remember phone number that tells how many frets are between each note.