What stat determines how many spells are drawn when you use draw?

[TheSpoonyBard]

Or an exploitable game mechanic that makes it easier to gain access to Diablos as soon as you receive the Magical Lamp.

[The Last Oath]

Preety sure when I had a very high mag stat for quistis on one play-over she was drawing 7-9 spells per draw. When zell, who I focused on increasing his str and vit, drew magic he got 1-4 very more often then he did anything above 7 and never 9.