Brenda meets her there! They are not the best team present.

Margaret tries her best but doesn't mind when they lose; she picked her team on the basis of it having Brenda on it and it fulfilled that criterion successfully.

"They have these every week but I don't go every week."

"I've got too much on my plate to go more than once in a while; this wasn't quite back-to-back with robotics club but it was pretty close."

"I don't know how anybody comes to these every time they have them, honestly, they're fun but they'd get samey - like, the questions are all different, but everything else -"

"Competitiveness? Excuse to hang out with friends?" Shrug.

"Maybe some people are just really attached to having a routine."

"I like the routine I've got but that's more that I like all the individual things I do a lot of."

"Yeah, it's different. I'm gonna go get some fries, I didn't have enough dinner. See you later?"

"See you later!"

Trivia felt like it took longer than it did; she's surprised to see when she gets home that she still has some time to spare. She re-enchants the box again the same as last time, except this time she takes careful measurements of the interior heights of all four sides first. What happens to the inevitable millimeter-scale differences when the box is expanded and then reverted?

The discrepancies in lengths of box sides are twice as big, indicating that the whole thing has scaled.

That's pretty neat. She fills the expanded box with wads of crumpled paper (exactly fourteen of them, as it happens), leaving the top open. Then she disenchants the box.

Wads of paper fountain into the air. When she checks, one has clipped partly through the bottom of the box, embedding itself in the cardboard.

Well that's extremely scary. Are the other thirteen all present and accounted for, at least? Does the outside of the bottom of the box have paper sticking out of it?

The outside has a little corner of paper sticking through it. All the others either popped out of the box or managed to stay or land inside it.

She had half expected, when she set up the experiment, to see some of the pieces of paper disappear into nothing, but this is way worse. She's done with magic for tonight, but not with science. If she tugs gently on either side of the paper, does it come out of the cardboard?

Nope.

Once Margaret is over the mental image of what if that piece of paper had been somebody's hand, it occurs to her that fusing things into other things could, in theory, have some kind of practical use. She probably won't be pursuing that, since 1) it's more likely to have applications for heavy industry than for consumer goods and 2) yikes, but maybe at some point somebody else will. She gets a knife and carefully cuts into the place where paper meets cardboard, trying to determine what the interior structure is like. Did some cardboard get deleted to make room for paper, or vice versa, or a bit of each?

If she'd thought to weigh the box perhaps she could determine if anything was deleted at all. As it is it looks like it was made that way, like during the pulping process when all the cellulose was being formed into shapes this bit and that bit were arranged like so and then somehow the paper was bleached separately.

Sadly she did not think to weigh the box. She spends the rest of the night on incantation design, reworking the space-folding spell to start with "Make the inside of this box twice as large in the dimension currently parallel to the direction of gravity". It's a mouthful, but it doesn't require marking the box first and it should work unless she has to enchant while in a centrifuge or outer space. 

When she gets around to trying the new version, it's a different evening and she has a different non-cut-up box. The box is still taped shut for casting, to make the distinction between inside and outside as clear as possible.

The box doesn't sit perfectly level and its expansion in the dimension currently parallel to the direction of gravity is angled a little oddly relative to its sides, but the spell works.

Does having "currently" in there let her pick the box up and tip it and so forth?

Yes, that still behaves.

Then that's alright, because if and when she starts selling Boxes of Holding she'll get nice ones that sit flat. She disenchants the one she's got now.

It's time for something completely different and potentially vertigo-inducing. She tapes and enchants the box again, replacing the specification of which dimension with a simple "all three dimensions".

Once she opens the box it gets very confused and there is a hard-to-parse squidge of spatial anomaly before the spell breaks (on all three dimension, not just the two which are complicated by having an end opened to an aperture of fixed size).