Although Vaan had already absorbed mana equal to an Early-stage Senior Witch, the accumulated amount in his Upper Dantian was less than a Peak-stage True Witch.
However, that didn't mean he lost a portion of the mana.
As the nebulous cloud of mana followed the cosmic flow in Vaan's Upper Dantian, it continuously refined itself into higher-quality refined mana, strengthening the magic power.
Thus, even if he only had the mana supply of Peak-stage True Witch, its output was equivalent to an Early-stage Senior Witch—or possibly even stronger.
However, this was only the initial result of Vaan's short cultivation.
His magic power would keep increasing as he continued refining nebulous mana clouds and strengthening his mana core. And the stronger his mana core became, the faster the refinement and recovery of mana.
In other words, the gap between Vaan and other wizards and witches at the same rank would only widen over time.