You need to choose where your posts are stored.

That's the public outbox/home option. You need to pick one, otherwise your posts just go to random places and its REALLY hard to find them.

Then you have to choose a relay that people can send you their reactions, zaps, replies, etc. That's your Public Inbox relays.

You need to choose a MAXIMUM of 3 in each: 3 outbox and 3 inbox. 1 is too little because many relays go off line here and there. 2 is good for resiliency and 3 makes sure at least one of your relays are always there.