Historically, they have typically awarded some combination of 5 or 6 on and 2-3 off. You get to designate 6 of those days as "golden", and they're not supposed to be touched by scheduling. Min of 11 days off a month, which is all you'll get.
Looking at the awards for last month, it appears that folks are taking advantage of PBS and requesting to bunch up days into a large group (so, say, work 4, 5, or 6 on and then 1 off for a couple weeks and then take a bunch of days off).
I'm not experienced with that and can't say how often it's awarded or how senior it goes.