"I'm referring to when something starts dividing!"
"Something starts doing math?"
"...Yes!"
While I enjoy the main canon having magic that can be treated like a science, I also enjoy magic that can have conditions like phases of the moon for purely poetic reasons (gravitational pull has nothing to do with this).
I wanted permanent changes to be both possible and reversable, but they couldn't be so convenient as to make everyone ask "why didn't she just do that for the party, then?"
It's because moon.
So there.