Ask your ual buddies about it. From what I understand it's why a lot of people have been avoiding rsv on wb fleets (and why it goes so jr.). Have 3 days of availability but theres a 6 day trip? They can give it to you (vs being forced to do a greenslip here or breaking up the trip).

Basically you get a few days off a month that are hard days that they cant touch. 6 of em. But they can move the rest. No thanks to that .

That's my rudimentary understanding.