Okay, did some digging on some old Phase Connect viewing numbers I'd saved. Gen 3 debuted late December 2023, these numbers are one week after debut:
And Phase Invaders debuted May 2023, these are the sub numbers are on the day of debut:
View attachment 78818
I know I've posted the CCV during both sets of debuts, which I might dig up later if anyone wants them.
So V4 Mirai's 40K subs for predebut is huge, and 3K is fairly small (but a talent could build from that with hard work).
Back to Nenelove's question about botting - I don't want to claim without evidence that the higher numbers are from botting. Brave Group loves spending money to get clout, and paying for a big advertising campaign for huge debut numbers is something I could see Brave group doing. The best way to see how things pan out is to see what the debut CCV is like, if stuff like chat speed matches, and how the talents fare in the weeks after debut.