Under CCP art. 42.18 §8(d), when sentences involve the stacking of pre- and post-1987 offenses, those sentences should be treated as one unit for the purpose of determining when a defendant is eligible for release on mandatory supervision for all sentences that are eligible for mandatory supervision. Under CCP art. 42.18 §8(c), a release date for mandatory supervision for all the mandatory-supervision-eligible sentences would be calculated as a unit, and then add the length of any mandatory-supervision-ineligible sentences to arrive at a final mandatory supervision release date. Ex parte Forward, AP-75,705.