If we could get a decent enlargement of that overhead shot, we could divide it into sections and actually count heads. That would give us a better estimate of the size than just guessing. I don't mind counting.
DC cops have a system, They look at the total area filled, then give each person standing 10 square feet (I think) to allow for non crowding, aisles, etc.
They give sitting people 20 sq feet I think. Assume at 700 feet by 300 feet, that's 210,000 sq ft; some standing, some sitting, minus the stage, minus those big open areas outside the circle, It's about 10K people +/-.
All in all, a big no show.
.....And how many are media and how many are just tourists, coming and going, who are watching the "show!?"