The letter means that "when he is released", he is to report to the probation Office (by web portal) within 30 days of that. He will most likely not be released earlier than his out-date. That pretty much never happens. One small bit of advice, please tell him that once is is out, that he cannot take the probation officer lightly. He knows what he can and cannot do, where he can and cannot go... and just lay low.
https://www.inmateaid.com/ask-the-inmate/my-husband-is-currently-serving-an-11-and-a-half-month-23-month-sentence-in#answer
Accepted Answer Date Created: September 20,2016