When the club asks you to fill out the information in the About tab of the Manage Account section of the Members Only Tab it is serving a purpose. The primary contact is usually the person who signed up. The secondary person is any other adult who lives in your home. There is even room for more adults if you are a multigenerational household after you have added the 2 names and hit next.
What does this do? It helps all the interest group chair people keep an accurate count of who will be attending the event. It saves time and confusion trying to figure out who the second person in a household is who is coming to an event. That way if say Sophia was coming to a luncheon and her partner Raphael wanted to join she could sign up both of them by name and the nametag person would have an accurate list of who would be attending. This also holds for any event that you sign up for in the calendar.
Just a bit of housekeeping but thank you for helping the club run more efficiently.