Permissions are used to specify criteria for being able to view/edit data types (that is, data that’s stored in the database), and not for pages.
To keep people out from a page, you need to use Actions such as redirect, and Only if to make sure only the right people have access. Note that scripts are not run immediately, and page elements will usually be visible for a second until it had has time to redirect the user. So you might want to use Conditions as well, to keep sensitive elements hidden from view.
If all this sounds like greek, let me know, and I’ll elaborate