As an aside, this thing called "an individual's Magical Energy" as used by Blue in a foolish yet clever manner. To use a simile, it was like driving a car for 1000 km on 1 L of gas.
Also, the capacity of Ciel was ridiculously large. If a regular magus' gas tank was 40, then Ciel's was more than 4000. She truly deserved the name Miss Glutton.

talk. - Magical Energy