Not being there, I don’t know the exact stage dimensions, but let’s rough it out.
The field, including end zones and excluding end/side aprons, is 162’ x 360’ = 58,320 s.f. If there was 25% of that space occupied by the stage, barricades, sound equipment, etc. we’re left with 43,740 sf. Most event planners will tell you it’s customary for 6 sf of standing space per person and if there were seats that probably goes up to 10 sf per. So the number on the field would be somewhere between 4,000 and 8,000.
If you squeezed the staging down to 10% and allowed only 4 sf per person it still would be just 13,000 people. Not as many as the naked eye might think.
So 88k total sounds about right. No more than that.
I know. I know. You were told there would be no math.