First Step Act changed this and it could technically be 50% (12.5 years) although I don't personally think it will be in SBF's case.
See this guys comment...
https://news.ycombinator.com/item?id=39856162
and a million others correcting the "85%" meme that HN parrots incessantly (not sure why anyone would expect programmers to be experts on federal incarceration nuances)