Tarot Simple Yes/No spread-I don't get it?

[FairyCrystal]

I don't get this one, in the book from the Green Witch Tarot. Am I reading it wrong or wot?

This is the explanation:
-Ask a question that can be answered with yes or no.
-Pull the card to create a stack, stopping when an ace or the Witch (Magician) is pulled or upon counting out the 13th card.
-Start a 2nd stack, stopping with an ace, the Witch (Magician), or the 13th card, then create a 3rd stack the same way.

- If there are 3 aces (or 2 aces and the Witch) showing, the answer is YES.
If no aces or the Witch show, the answer is NO.
If there are 1 or 2 aces or the Witch, the answer is POSSIBLY YES, but read the other top cards for details.

Now I get this can work if you go for the 13th card, but if you continue till you get an ace or the Witch (Magician), you'd always get a YES? Or am I misreading this? I don't get it...

Also, is this of value? I mean, even if you go for the 13th card 3x, the chances of getting either a YES or a NO are slim?

From the top of the deck start pulling cards, continue until an Ace or Magician card turns up within the 13 cards. If none of these show up, you use the 13th card.
I think it may be that the wording in the book hasn't been made clear enough. It does seem a touch ambiguous but this is how I'd read it;-
If an Ace or the Magician card does not show up by the time you reach card 13, you take that card instead and start your next pull of 13.

Don't know if I'm making sense.

[FairyCrystal]

Yeah, that makes a lot more sense, haha. Thank you.
Reading through it again -with your feedback in mind- I see how the author meant that. Cheers!