As Vaan trained in the Way of the Formless Dragon, he consumed a large number of mana stones only to produce a small amount of dragon aura.
However, dragon aura was much denser than the normal aura. Thus, even if the dragon aura was smaller, the power was still comparable to a greater normal aura.
Nevertheless, his dragon aura wasn't the only thing improving.
After performing the required set of physical movements a few hundred times with increasing tempo, Vaan began to feel the burn in his tired muscles.
Thus, he absorbed more mana and allowed it to nourish his body.
Ding!
…
Due to Vaan's high defense and strength, some benefits of practicing the Way of the Formless Dragon could not be seen.
Even so, his body still improved in a way that also increased his speed.