When an inmate gets out of the DOC depends on the prison the inmate is in and also the state in which the prison is in. The charges the inmate is charged is also another matter to be considered as different inmates have different charges.
It really depends on a number of factors. An inmate can earn a certain percentage of custody credits toward their sentence in order to be eligible for early release. But for some offenses, usually serious or violent offenses, the percentage of custody credits an inmate can earn toward their sentence is limited. So the nature of the conviction factors into when the inmate gets released.
The inmate's release also depends on their disciplinary record while in prison and can result in a loss of conduct credits so that they end up serving everyday of the sentence imposed.
Again, depending on the conviction, before the inmate is released, the DOC may determine the inmate is a sexually violent predator where a petition is filed holding the inmate until a civil committment hearing can be conducted to determine whether the inmate qualifies.
Whether the inmate has a "hold" is also a factor. An immigration hold usually means the inmate will be deported, and a hold from another county or state usually means the inmate has additional cases, in which case he or she won't be released, but instead transported to wherever the unresolved cases are.