They curtained off areas so empty seats would not be visible.
Being generous, maybe the one had 1500-2000 total including 200-300 media swampers.
Trump could draw 2000 people with a one hour notice, in McKeesport, PA.
McKeesport, PA is a beat up demonRAT shithole {sorry I worked there once}, and any Trump supporters that live there, don't have Trump signs or bumpers stickers, and would not admit it at the local gin joints.
And Trump could still get 2000 people at the Mckeesport Tigers Football Stadium {with one hour notice, and a single tweet}. It would require armed guards for the parked cars, but in W. PA we do have a load of arms.