Welcome to FlyerTalk, af1010.

For people who sign up online and provide a valid email address, you get 3 miles/$ from AAdvantage Dining from your first dine, and 5 miles/$ from AAdvantage Dining starting with your 11th or 12th dine. You get those 3 miles/$ or 5 miles/$ independent of what kind of card you use (as long as you've registered that card with AAdvantage Dining).

That is on top of, and separate, from the 1 mile/$ that you earn from the Citi AAdvantage MC.

(There's nothing that says you have to couple an AAdvantage MC with AAdvantage Dining. If you also have a cashback card, for example, you could register that card also with AAdvantage Dining. Then when you used the cashback card, you'd still earn the 3 mils/$ or 5 miles/$ from AAdvantage Dining, but instead of the extra 1 mile/$ from the AAdvantage MC you'd earn cashback through the cashback card.)

Btw, the AAdvantage Dining program is discussed in the iDine / Rewards Network forum: