For those accepted from the Caltech waitlist, when and how?

I got waitlisted for Caltech. Since its my #1 choice, I immediately chose to keep in the waitlist and submitted a letter and some supporting documents. The deadline for Regular Decision acceptances to submit their SIR is May 1st (this Friday).

For those who were accepted from the waitlist, when were you notified relative to the RD SIR deadline? The school says it can finalize waitlist decisions anytime between May 1st - July 15th, which is a pretty large gap of time but I’m willing to wait for it. I just want to know from previous years when waitlist announcements were most commonly given so I’ll be super careful with checking my account. Also, in what form do they message you if you get accepted? Do they email or call or text you?