Yet according to the official attendance and capacity there's only a few hundreds seats empty. With NFL owners it looks like they're going down the NFL route of calculating attendances.
That’s not how it works. The ‘official attendances’ assume everyone who has bought a ticket and all season ticket owners are present. There is an ‘actual attendance’ figure which is required by the Police as part of their management of the crowd. A couple of years ago the police forces responsible for policing in the Premier League were suggesting attendances were overstated by as much as 20%