When it comes to standby loading, revenue standby come first, in order of priority. Then non-revs are loaded, by pass priority. Non-rev standby's should not be loaded in J unless Y is full.

Where Y is full, and non-revs are not going to make it on, the usual practice would be to offer operational upgrades either to full fare Y's or to SE's, before clearing the standby list. But where the flight is open enough to handle the non-rev's, with some overflow to J, the high pass priority non-rev's would get the J seats.