(4)The period during which a person is absent from prison on leave in pursuance of a furlough order shall be reckoned as a part of the period of imprisonment to which he was sentenced :Provided that in cases where the furlough order is revoked under sub-section (2) for failure to observe any of the conditions of furlough, the period of such absence from prison in pursuance of such order shall not be so reckoned as a part of the period of imprisonment.
