I also did the assessment, they have lots to choose from. They are watching you and secretive on who they want - if they see you and like you -
If they like you and want to interview you they will call you and progress you telling you in private. I was asked for interview in private and many were told possible call back later approx. 8 were interviewed on the day.
strange operation on how they do select but an enjoyable day out.
Be yourself ......
They cannot interview all or give sim checks to all. So do not believe that everyone will get interviewed on the day Interview's for 6- 8 people on the day and some were invited approx. 3 for simulator the next day and others invited later. Not sure if those promised a interview at a later date has happened or not.
All the best