Just FYI, from the FTD stuff. They won't get away with "reasonable time".

§ 117.21 Reserve status.
(a) Unless specifically designated as airport/standby or short-call reserve by the certificate holder, all reserve is considered long-call reserve.
(b) Any reserve that meets the definition of airport/standby reserve must be designated as airport/standby reserve. For airport/standby reserve, all time spent in a reserve status is part of the flightcrew member’s flight duty period.