Imagine Zuckerberg selling his Facebook shares, then claiming to flee from USA for not willing to give the data from the Facebook to the FBI. Which of course Facebook (just like any other competitor like Google and Microsoft) gives since it's all regulated by the law:
The last time it was 12% (which is all he had of Vk stocks). There's no info of money amount involved, but I susoect if it was something ridiculously small we'd hear about that already from Durov himself, and estimate of how much it was worth is $M300-400.
https://www.facebook.com/about/government_requests
Disclaimer: I don't know how much Durov actually sold. Any additional info welcome.