Is bra size 30 AA a training size?

No, it would be considered just another bra size. A 30AA means your ribcage equals 30 inches, and your bust measures 30 inches as well, since an AA cup means there is a 0 inch difference between the two measurements.

Training Bras do not have a bra size attached to them, but are just a piece of fabric and elastic around the bottom, so girls get used to wearing something on their chest.