At the time of booking if all berths are exhausted in GN quota and PQ still shows availability then those unbooked PQ berths will be allotted to GN quota pax.
In this case there was no berth in GN quota so the system checked if PQ is having any vacant berth. Luckily PQ showed 1 Available so that 1 berth is allotted to the 1st passenger whereas the 2nd passenger will be put on GNWL 1 as now both GN and PQ quota is exhausted.
A point to note here is that...
more... although confirmed berth(s) from PQ is allotted to GN quota but GN quota pax will never be put into PQ WL and will always be put in GNWL.