Ten percent would be the end of the month of June. However, there is no way of knowing for certain if he would be released since that is only an estimate. You are looking for a definite date and unfortunately no one can provide that to you. I sympathize as this uncertainty is difficult for both you and him.
This is not intended as individual legal advice and there is no attorney client relationship established by this answer. It is advisable that you seek individualized legal assistance. This is not a substitute for hiring an attorney.
The percentage person at the jail will determine when he will be released. The percentage is computed often sometimes on a daily basis. So it really depends on the total population. The judge has no say in the matter, the judge can only estimate it like the rest of us. I would guess sometime between 30 to 60 days would be more realistic.
The response above is not intended as legal advice since it’s impracticable to provide thorough, accurate advice based upon the query without additional details. It is highly recommended that one should seek advice from a criminal defense attorney licensed in your jurisdiction by setting up a confidential meeting. Moreover, this response does not constitute the creation of an attorney-client relationship since this message is not a confidential communication because it was posted on a public website, thereby publicly disclosing the information, which is another reason to setup a confidential meeting with an attorney.