If you want to change inherited access control list (ACL) entries for a folder or file, you must make the inherited entries explicit.
Select your server in the Server app sidebar, then click Storage.
Select the folder or file whose access permissions you want to change, then click the Action pop-up menu , then choose Edit Permissions.
In the Edit Permissions dialog, click the Action pop-up menu , then choose Make Inherited Entries Explicit.
You can now edit the ACL entries.