When the judge says, "time served", that means that whatever time he has accumulated awaiting the sentencing, is applied to the sentence. He should get with his counselor or case manager to make sure that he is getting proper calculation - they should then be able to give him a new "out date".
https://www.inmateaid.com/ask-the-inmate/my-boyfriend-was-sentenced-to-1yr-and-at-his-sentencing-i-heard-the-judge-say-1yr-with-credit-for-time-served-when-he-requested-his-release-date-it-didnt-reflect-the-time-served-instead-it-showed-his-release-date-as-a-year-from-his-sentencing-how-does-he-.amp#answer
Accepted Answer Date Created: July 31,2014