Why on page WordPress site SEO title and page title is different using yoast?

I am using yoast SEO plugin for my WordPress site. Configuring when I change my webpage seo title it automatically change my page title I don’t want to show that.

eg.

Page title. About us

SEO title. About us – Mukta Art

I need to show on my page only "About us" title instead of SEO title. When I edit page title not change update and when ch