He probably just means from suppressing the anti-mask, anti-vaxx shit. Prolly cost him some right wing advertisers.

He doesn't seem to explain what covid related content they were told to take down. Probably dumb anti-science shit.

Zuckerberg also expressed regret for Meta’s downplaying of content related to coverage by the New York Post about Hunter Biden ahead of the 2020 election that the FBI warned may have been rooted in a Russian disinformation operation.
“It’s since been made clear that the reporting was not Russian disinformation, and in retrospect, we shouldn’t have demoted the story,” he wrote.

But he's kinda right about this.