Confused with Sentence

My question involves criminal law for the state of: New Jersey

I have a friend that is currently in prison, she was charge with violation of probation & possession of marijuana and intent to deliever. the day of sentence she was told that she was goin to do a 3 year flat come to find out is not a 3 year flat its a 3 year mandatory/minimum, My questions is what is the difference between the two sentences and how long does she have to do b4 being release??

A reference to "three years flat" would typically mean that you serve three years and it's all over.

A three year mandatory minimum would mean that you must serve at least three years in prison as part of your sentence, but that you could potentially serve more.

We have no way of determining what her sentence was; she should have documentation that indicates her earliest possible release date, or be able to obtain it from the prison.