Anki: Confused about what review ahead is

I am learning how to use Anki to learn Japanese. I want to check that I understand review ahead clearly, since I am getting confused by the manual.

Let’s say you review ahead by 1 week and you review ahead on the date 7/20. Card A is due on 7/21 and the beginning of its interval was 4/21. Because you review this card super close to its original due date, the new interval will be similar to the interval that would have been created had you reviewed the card on the original due date. Card B is due on 7/25 and the beginning of its interval is 7/19. Because you review this card so close to the beginning of its interval, Anki creates a new interval similar to the 7/19-7/25 interval. I guess the review ahead option is designed this way in order to keep the new growth of a card as similar as possible to the growth that would have taken place had you not reviewed ahead.

If you review ahead multiple times, it is bad because for cards where you keep reviewing very close to the beginning of its interval, the card’s intervals will not get bigger.

If there is any part of my explanation that is wrong, could someone please tell me? And if there are major characteristics of review ahead that I should know about, it would be great if someone could tell me. Thank you.