He is going to federal prison, which means he needs to serve 85% of his sentence or 21.25 years minimum.
Not according to CNN:
"“SBF may serve as little as 12.5 years, if he gets all of the jailhouse credit available to him,” Mitchell Epner, a former federal prosecutor, told CNN.
Since 2018, however, nonviolent federal inmates can reduce their sentence by as much as 50% under prison reform legislation known as the First Step Act."