It truly is a beautiful symbol, one can ponder it for hours. I'm not sure what the letters on the small barbs mean. If I recall, DuQuette doesn't say, and then I neglected to come back to it, I forgot.
If you're studying his
Understanding I found it useful to draw it out in stages like he does, it makes things clearer. You can also arrange the cards in the form of the petals, a fascinating exercise. In any case, there is a reason it's right at the beginning of the book, as in many ways it sets the stage for what comes after, and is important for how many cards play off the others.
Understanding is a book that should give you a good base with which to continue, and it doesn't have a whole lot of Qabalah in it, but it
is tier-structured so I don't recommend you skip that chapter.
And I'll be a nag again... Qabalah isn't difficult, and will open up the deck in ways you would never imagine. Try
All you need is a few basics, and then study of the Thoth becomes study of Qabalah, since it is built by it.