Yea with a full helicopter (I'd say 6 or so) and possibly others went up like DC said, it is not entirely possible you have 12 or more there easily. I never tried to count but when I seen the chopper that was what I assumed when watching the show.

At this point it is just hard to figure out Harry Potter, did he just have some illness and die? Did he eat something tainted? They left a lot to be answered which is way I like shows like that.