Must an inmate complete 85% of their time before being released?
Many states have laws that require inmates to serve at least 85% of their original sentence. Without knowing what state you are in, it is impossible to say what the law is in your state. In general, states that have these laws will still allow an inmate to "gain" time for good behavior, but that amount of time deducted from his sentence must be, overall, no more than 15% of his original sentence. When released early, the inmate is still under the supervision of the corrections department -on parole- until he has reached the term of the original sentence.
Here are a couple of websites where you can explore this concept further and, possibly, find out the circumstances in your particular state.