Seems like this is not a "brand new" computer since a brand new Mac will greet the user with Setup Assistant to allow you to configure & customize macOS including creating the first macOS user account for new owner. Many computer refurbishers will use the "User" login for refurbished computers because it is generic and usable by anyone. Refurbishers create a user account in order to make sure the OS is updated and to install third party apps and customize settings for people.