WAIT: Why does the title of the 404 page show the number 1?

Why does the title of the 404 page show the number 1?
Is my setting incorrectly caused?
How to customize the 404 page template correctly?

Hi @dichen,

what do you mean by “title”? The Page title? Did you set something in Page Settings » SEO » Title?
Which bricks version are you using?