We can't tell from your screenshot what the ticket number is, which should be visible in the URL. If it's less then 23 then it's definitely a demo ticket which didn't get properly deleted. Otherwise it might be related to using demo users in conjunction with a new ticket.
You should be able to delete the ticket entirely by going to the tickets overview page and then select Delete tickets from the actions menu (after selecting the ticket). To do this you'll either need to be the Built-in admin or have the Delete Tickets permission as an agent.