
Explanation:
Box 1: All users
"Enable for users to sign-in" is selected and "User assignment required" is set to No. Any user can login using the app url.
Box 2: Only users listed on the users and groups blade
User assignment required - This option does not affect whether or not an application appears on My Apps. To show the application there, assign an appropriate user or group to the application.
https://docs.microsoft.com/en-us/azure/active-directory/manage-apps/add-application-portal- configure