In addition to the site saying "first come, first served", it also said the event is purely informational in nature and no interviews will be conducted. They could certainly weed people out if they wanted, but they'd just be inviting the most qualified people to, what, see if they care enough to show up for a tour?

Sounds like they're going to go one by one in order of who signed up looking to weed out things like double entries, inaccurate profile ID #s that don't match anything in the database, etc, until the event is full. They also have to go through and provide the additional invites to the limited-space-tours on 2 May and 3 May that the registration asked about.

Hopefully that won't take all the way until April 10th, though.