Having tapped everyone with Share Language - including Broom, once Broom reminded Keltham of his existence - Keltham speaks forth again:
"The first thing to do in this experiment... is something I expect you'll all find way too natural, namely, don't say anything and control your facial expressions. That's not the usual rule in this classroom, but in this case I want you to confront a problem separately and without leaking information to each other, so no comments out loud on what I'm about to do or say here. If you want to say something to me, or have a question, say 'Message' and then use Message."
Keltham goes to the wall, casts Prestidigitation, and draws three Baseline numbers via color-changing the wall's surface. Possibly using Prestidigitation all the time will help train magic use to where it becomes more innate and reflexive for him? Though he should actually check that concept with Carissa at some point, because it's a time-costly experiment.
The Baseline numbers that Keltham draws are 2, 4, 6.
Next to those three integers, the simple Baseline symbol for 'yes' in the sense of 'yes, that worked' or 'yes, that is an instance of the category' or 'this test returned yes for whatever it tests for'.
(It should be immediately apparent that Baseline numbers are both easier to draw, and more visually distinguishable, than Taldane digits. Just one more little reminder that almost everything about dath ilan was designed and not just allowed to happen.)