(a) In the discretion of the Director of the Department of Corrections, a prisoner may be allowed meritorious good time credit for performing exceptionally meritorious service or performing duties of outstanding importance in connection with institutional operations.
(b) Meritorious good time credits authorized by this section shall be applied to the person’s minimum term of imprisonment to determine the date of eligibility for release on parole and to the person’s maximum term of imprisonment to determine the date when release on parole becomes mandatory.