When determining the statutory maximum sentence on revocation, should courts consult current law or only the law at the time of the underlying offense?

1. When determining the statutory maximum sentence on revocation, should courts consult current law or only the law at the time of the underlying offense? Specifically, when a defendant is sentenced on an offense prior to the First Step Act but whose supervised release, for that offense, is later revoked after the First Step Act, does he receive the benefit of the First Step Act when determining his underlying felony classification and the statutory maximum revocation sentence?