Originally Posted by Apieinthesky

As FlyMeToTheLooneyBin said, it's only flown miles, or more precisely,base miles or EQMs. Since elites get a 500 mile minimum, they will get more than the flown miles for flights under 500 miles.

Also, before when all miles counted (and now, still), AA keeps track of all the miles you earned. In your AA account, there is a counter called "Million Miler Balance." Thus, you do not need to keep all your earned miles. The system will automatically keep track, even if you redeem them.