What does this Default Line do? And how do I get rid of it?

What does this Default Line do? And how do I get rid of it?


Won't allow me to publish without connecting it to something, and I don't see it's inherent purpose for the context of a 'button'.

Also If I could receive some support integrating with Whatsapp if possible? Because every time I go to integrate it, its prompting me to assign a new number despite already selecting my Whatsapp Business Profile that already has a number assigned.