All sentences (except for "life") come with "good time credits". Usually this is 15% of the length of the sentence. You can only lose these good time credits for breaking the rules while incarcerated.
There is a parole system for most state prisons but the only inmates eligible must have it designated on the Judgement and Commitment document. Federal prison does not have parole but they do have RDAP. RDAP is the Residential Drug Abuse Program. Inmates that are eligible take a nine month course and get 12 months off their sentence plus at least six months of halfway house.
https://www.inmateaid.com/ask-the-inmate/do-u-get-a-reduce-sentence-for-good-behavior#answer
Accepted Answer Date Created: June 18,2015