The “Opt in” entry just shows that you have opted in this month and that it cost you nothing to opt in.
The credits that you earned in November will show as a seperate entry once they have been credited.
Your credits that you have earned for November will show on your live billing some time in the next week.
This has been confirmed by the team running the offer.
What credit you earn in any month is deducted from your next months bill, that usually happens between the 5th and the 10th of the next month
See this post from yesterday for a fuller explanation: