The sheriff in charge of a county jail may, upon a consideration of the quality and amount of work done in the kitchen, in the jail offices, on the jail premises, or elsewhere, allow reductions of inmates' sentences as follows:
(A) On sentences of ninety days or less, up to three days for each thirty days of sentence;
(B) On sentences longer than ninety days but not longer than six months, up to four days for each thirty days of sentence;
(C) On sentences longer than six months, up to five days for each thirty days of sentence.
The reduction of the inmate's sentence shall become effective only upon the written concurrence of the presiding or sentencing judge or magistrate of the court where the sentence was imposed.
This section shall in no way restrict any other powers vested in the presiding or sentencing judge or magistrate of the court where the sentence was imposed.