About 18.8 million entries were excluded from the data because they did not start with the 'zz' prefix and appeared unrelated to coordination; most of those related to cheating on cyber tasks.

There were another ~18.8 million entries that were excluded, that did not start with the conventional prefix ‘zz’ and appeared not to be about coordination. The vast majority of those, too, related to cheating on cyber tasks.

https://thezvi.substack.com/p/metr-and-redwood-offer-holy-postmortem