From the paper, it's four people from the NSD:

« We analyzed data for four of the eight subjects who completed all imaging sessions (subj01, subj02, subj05, and subj07 »

P3 here: https://www.biorxiv.org/content/biorxiv/early/2022/11/21/202...

I am pretty pretty sure that this is just per person. so all it does is categorize complex brain patterns of one person into 10 category numbers and then do some hula hoop to display the numbers.