there is apparently a fixed rule -- x hours rest for y hours of work.

however, staffing on the new CX830/831 and other super long haul routes is apparently so finely cut that even minor delays in take off or en route would violate this rule.

the article also mentions dissatisfaction re: the FA resting environment -- how lights can't be turned on so they cannot even read a magazine to relax, how it's difficult to fall asleep -- and comparisons are drawn with the resting area for pilots, a much more luxurious setting with a proper bed, tv, etc.