I think “shortly before” is a fair interpretation of the following quote:
> …'hey, just so you know, you should be on high alert. We thought there was a lot of Russian propaganda in the 2016 election, we have it on notice that basically there's about to be some kind of dump that's similar to that'."
> He said the FBI did not warn Facebook about the Biden story in particular - only that Facebook thought it "fit that pattern".
The timing (“there’s about to be… [a] dump”) sounds like an important part of the identified pattern, or else it wouldn’t have been mentioned in the quote.
Why do you think it was "shortly"? Zuckerberg gave no details on the timing of the FBI's warning.