He will most probably have to finish the remainder of his original sentence. If he didn't catch another charge, he should be out in March or thereabouts.
https://www.inmateaid.com/ask-the-inmate/yes-i-have-a-friend-whose-son-is-on-probation-and-he-was-locked-up-again-i-was-wondering-will-he-go-back-to-prison-or-since-his-probation-is-over-march-2019-they-will-not-extend-his-probation#answer
Accepted Answer Date Created: February 09,2019