You might notice that when logging in to your application using Google OAuth, you see this: 
Magic functions as a wrapper around the social logins you set up in your dashboard. When you initially configured social login via Google in your Magic dashboard, you copied the redirect URI, which you then pasted in the Google Console.
Because of this interaction between Magic's API and Google, there is not currently a way to change the name of the app in the Google Login authorization screen. However, if your users click on <magic.link> in the screenshot above, they will see the email address associated with your app's Magic account.