As you move up the fingerboard (or as the notes get higher), the spacing between each note gets progressively smaller. The difference between a whole step in first position and a whole step in thumb position is vastly different - the whole step in thumb position is almost half the size as the one in first position.
This is something you have to practice to get a feel for under your hands, so that’s what we’ll be doing in this lesson. As you’ll find out, the spacing between 1st and 4th position isn’t too different, but it’s enough that you will play out of tune if you don’t adjust.
As you practice these exercises, I would suggest you play along with a tuner in front of you or with the recording I’ve included so you can monitor your intonation and adjust as needed.