One of two possibilities could have happened here; either the bonus from Focus passed via Yuna to the Aeon (not 100% sure about that), or the hidden battles bonus occurred.

On the first front Focus effectively increases both your Magic and Magic Defense. Rather than affecting the base stats it adds a bonus during the damage calculations. It stacks up to five times and lasts for the whole of the battle until the target is killed or petrified. On the second front there is a hidden bonus procured on Summons during the game based on the number of battles you have fought, which follows Yuna's sphere grid in terms of gains quite closely. This is to make sure the Summons remain strong throughout the game even if you fail to level-up Yuna.