(5)The time during which a child is absent from a special school or children's home in pursuance of a licence granted under this section shall be deemed to be part of the time for which he is liable to be kept in custody in the special school or children's home:Provided that when a child has failed to return to the special school or children's home on the licence being revoked or forfeited, the time which elapses after his failure so to return shall be excluded in computing the time during which he is liable to be kept in custody.
