Each person convicted of an offense against the state, which was committed prior to July 1, 1986, and confined in a penal or correctional institution for a definite term other than for life, whose record of conduct shows that he has faithfully observed all the rules and has not been subject to punishment, is entitled to a deduction from the term of his sentence beginning with the day on which the sentence starts to run as follows:
When two (2) or more consecutive sentences are served, the basis upon which the deduction is computed is the aggregate of several sentences.
In addition, those inmates doing an outstanding job, may be awarded industrial or meritorious goodtime under rules adopted by the state board of correction, not to exceed five (5) days per month.
Inmates performing exceptionally meritorious or outstanding services under rules adopted by the state board of correction may be awarded a lump sum of goodtime. The number of days awarded may not exceed the regulatory maximum.
Idaho Code § 20-101A