"Whether they go down by half depends on what the scale means. Mine went from 3 to 2, because I'm taking the 1 of the scale to mean that something absolutely can't happen, and equal intervals to represent equal amounts of chance, so halving the interval from 1 to 3 gets me the interval from 1 to 2. But it's fine if somebody else is interpreting their scale in some totally different way!"
"In fact, the aspect of Law I'd propose to govern here is that, when you have two events that both need to happen, the chance of that happening, cannot go up compared to the chance of just one event happening. Ione, for example, could've been tipped by the Whatchamacallit of Nethys that this coin is definitely going to land Abrogail's-face-up, in which case Ione could just give the exact same number she did before for the duck-lunch part. But even Ione's number shouldn't go up."
"By the way, Ione, thanks for being you, your mere presence here substantially expands the space of immediately relatable scenarios I can use for probability-theoretic examples."