請教小白兔等高人，關於I129表的一個問題

請教小白兔等高人，關於I129表的一個問題

If it is the 2nd extension after 6 years H1B.

In form I129, choose 2b in Part 2, question 2: Continuation of previously approved employment without change with the same employer.

Then what should be put in Part 2, question 3: If you checked Box 2b, 2c, 2d, 2e, or 2f, give the petition receipt number.
Should it be the first extension WAC receipt number or others?

Thanks a lot and have a happy Christmas.