Section 202(3)(b) in The Naval Ceremonial, Conditions Of Service And Miscellaneous Regulations, 1964
(b)If an officer proceeds on annual leave or combined leave (annual leave plus furlough) or on courses of instruction of less than 10 weeks' duration while holding an unpaid acting rank, the period spent on leave other than furlough, or such courses shall be considered as on duty for the purpose of conversion of unpaid acting rank into paid acting rank, provided he is borne against the same appointment on the date he qualifies for such conversion.