You're usually a very accurate poster on legal matters, but this contradicts the linked article:

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.

Federal prisoners generally can earn up to 54 days of time credit a year for good behavior, which could result in an approximately 15% reduction.

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.

Are you saying the article is wrong, or did you maybe not consider this possibility?