Clarify message a bit

Author: pjlast

docs/admin/permissions/api.mdx

@@ -99,7 +99,7 @@ You can call `setRepositoryPermissionsForUsers` repeatedly to set permissions fo
 
 ## Setting sub-repository permissions for users
 
-> NOTE: If no sub-repository permissions have been set for a repository, that repository is treated as not having sub-repo permissions enabled.
+> NOTE: If a user has no sub-repo permissions set for a specific repository (assuming that they have general access to the repository), they will have access to the entire repository contents.
 
 Sourcegraph supports permissions on a per-file/directory basis.