There is no just plain magic attack. Magic damage is calculated entirely based off the base damage of the spell (plus the Magic Damage+ if you have any), the difference between your INT and the target, and a bunch of multipliers, one of which is Magic Attack Bonus.I believe he meant total Magic Attack, not just MAB.
There is no stat just called Magic Attack, even though we have "Magic Attack Bonus." MAB is a damage multiplier.
Edit: White magic damage (Banish, holy, cure against unded) is caculated using MND instead of INT but the equation is otherwise the same as the one referred to above.