Anons already found the original tweet, see notables.
This was an actual tweet from 1/3/18, but has since been deleted.
http://didtrumptweetit.com/948362512315056129-2/
Updated sealed cases (indictements) count:
https://twitter.com/lonegreyhat/status/1069481239952928768
NOVEMBER: +5,387
68,615 Sealed Total
Starting around 27:35 Hannity brought up "Calm Before the Storm" and the media hype when POTUS said that. They went into a tangent on NoKo but ultimately POTUS expressed that it meant he wouldn't telegraph his moves.
I agree it's best we not bank on this count being an accurate reflection of sealed indictments. Even if the count is correct, it doesn't necessarily mean that all (or even most) are indictments. They can be sealed for several reasons.
Likewise, I've seen people claim they've debunked the entire claim, but I'm not in a position to be able to validate either side of this.
https://wmerthon6.wixsite.com/website-1/home/comprehensive-analysis-of-the-50k-sealed-indictment-claim