Sch 20B para 14
(1) If a person to whom paragraph 13 applies is serving a sentence with a custodial term of less than 12 months, it is the duty of the Secretary of State to release the person on licence as soon as the person would (but for the earlier release) have served the period found by adding— (a) one-half of the custodial term, and (b) the extension period. (2) If a person to whom paragraph 13 applies is serving a sentence with a custodial term of 12 months or more, it is the duty of the Secretary of State to release the person on licence as soon as the person would (but for the earlier release) have served the period found by adding— (a) three-quarters of the custodial term, and (b) the extension period.