"I'm...tempted to suggest changing something that would have consequences going really far back, and see if me or anyone else in the school disappears and is replaced by other people conceived under other conditions due to butterfly effect, but that's really dangerous and probably not warranted yet." 

"I don't know if it's losslessly reversible! I should try making the principal called Katheriine - or maybe just spell her name differently in a still conventional way, with a C or something - before I do anything I actually care about that I might want to put back."

"Yeah. --I'm going to put the print quality thing back, I googled the guy, and I don't want to let this timeline run too long before switching back."

"Yeah. Last time I just scratched it out."

Edie strikes it through in a single bold line. 

"I can't remember the other timeline anymore," she reports. "I can remember, like, facts I thought about in it, but the general history is no longer available to me." She immediately starts googling the guy from the other timeline's Supreme Court case. 

"I really wish it would let us keep notes."

"Yeah, that's annoying...okay, found him. Looks like he died in the same accident but nobody blamed it on anything out of the ordinary."

"Okay. So we didn't kill a dude, we're just rejiggering the lawsuit related decisions. - Where's Emily?"

"Talking to the art teacher about the syllabus."

"- was she definitely going to be doing that this morning, or did something about our commitment to print quality throw her off -"

"It wasn't, like, planned in advance, but it is highly unlikely to be print-quality-related, she wanted to customize one of the projects that was supposed to come up later in the term and the project was, like, sculpture-related, nothing to do with print."

"Okay. God this is making me so paranoid."

"You know what? That's fair." 

Emily drops into the seat beside Edie. "Hi guys, what's fair?" 

"Bella has a reality-bending notebook and only by the metaphorical grace of a hypothetical god did not accidentally kill a dude with it. So she's feeling paranoid." 

"Wait, what?"

"--Not a notebook, her copy of the student handbook," Edie corrects herself. 

"--For real? Like actual real magic?"

"Yeah. But it kind of retroactively changes everything including notes and memories except my memories apparently and if Edie is the one changing the book hers, so it's a little fraught to demonstrate, I can't exactly go 'do you remember those periods of time today where the school was bizarrely committed to print quality'."

"You are correct that I do not remember such a thing. Print quality?"

"I discovered this situation when, in response to the misprint on the cover of my student handbook, I added 'and commitment to print quality' to the our values section."

She peers at the cover of the handbook, then snorts. "Fair enough." 

"Yeah. And then Edie reacted to it and told me an anecdote about having to reprint all the yearbooks last year over a typo. Because of our commitment to print quality. And then I scratched it out and reckoned I'd been dreaming, but..."

"But. Well. You know, I've read crappy fantasy with worse magic than this in it, but I'd still rather have landed in not crappy fantasy with better magic than this in it. Have you tried to use the book to make everyone immortal yet? That would be, like, the opposite of accidentally killing somebody, if I woke up tomorrow and learned that everybody used to be not immortal I would super forgive you for changing my memories."

"Immortality isn't a school policy and we have been being careful, Emily, changes that big in the first hour is not what careful looks like."