This book: https://www.amazon.com/dp/B07MYFR2F9/ref=dp-kindle-redirect?_encoding=UTF8&btkr=1 has a description of how the tablature works in the beginning of the book and if you go to the "Look Inside..." section on the amazon link you can actually read that bit for free.

Also, it's great book and if you're interested in playing in the harmonic style I'd definitely recommend it.