Just out of interest do SO's get the same kind of roster as an FO/Captain?
No the rosters are not the same. S/Os mainly do long-haul and ultra long-haul flights, so there are more days off for them. In a nutshell... under HKG aviation law, there is a maximum amount of hours each pilot can fly annually (something around the 900 mark)... so when all an S/O does is fly long sectors that are probably 14-18 hours each, the number of flights they can do is reduced. This is opposed to a CN and F/O who can do regional flights that have fewer block hours, so legally they can be rostered to do more flights. Make sense?
The "divide by 4" concept you saw is how S/Os calculate the P2X hours that they put into their logbooks.