The IPv6 labels can be set when configuring the IPv6 address for controller A and controller B in the Dell Powervault Web UI. They cannot be changed. Only deleted and then re-added.
Dell does not have a change feature for the IPv6 label in the Web UI for the controller IPv6 address configuration. The address will need to be deleted and added back in, with the correct IPv6 label included.
The procedure is:
This should allow you to make the change to the IPv6 label for both controllers.