Absence under licence or on parole to be counted towards period of detention.

The time during which a person is absent from a borstal school under a licence or on parole shall be treated as part of the term of his detention in the school, provided that where that person has failed to return to the school on the licence being forfeited or revoked or when recalled from parole the time which elapses after his failure so to return shall be excluded in computing the term during which he is to be detained in the school.