If I read your question correctly, he was sentenced to a total of 2 years in custody with 50% for good time credits plus he already had credit for 25 days. Assuming these facts, he would be released after serving 11 months.
Lawyers generally don't like to do math, but I agree with my colleague. 25 days of credit so far means he did 13 days and gets credit for another 12. He'll still have to do just over 11 months.
If he was sentenced to "local prison," you can see his projected release date on sdsheriff.net.
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