So how does the 10% mileage thing work?
Does it have to be me travelling, or can I use it for travel booked for another?
This benefit applies to all miles redeemed from the primary cardmembers’ AAdvantage account – even if you book an award ticket for someone else.

Do I have to charge the taxes to my Citi card?
Your Citi / AAdvantage account must be open and active at the time of redemption but you are not required to charge AAdvantage Ticketing Service Charges for an award flight to the Citi / AAdvantage card to earn this benefit.

If I have two cards, can I get 20,000 miles back?
The maximum number of miles you can earn back in a calendar year is 10,000 per AAdvantage account regardless of the number of miles you redeem in that calendar year. Because this benefit is by AAdvantage account, you cannot accumulate 20,000 miles back per calendar year if you have two cards.