Update lib/charms/istio_beacon_k8s/v0/service_mesh.py

Co-authored-by: Andrew Scribner <[email protected]>

lib/charms/istio_beacon_k8s/v0/service_mesh.py

@@ -81,8 +81,10 @@
 )
 ```
 
-The labels argument should be a dict containing the Kubernetes labels which the client charm needs
-to apply to join the mesh.
+The labels argument is the dict of labels that indicate to the service mesh that a Pod should be subscribed to the mesh.
+These will be sent to each related ServiceMeshConsumer to be used by the charm for per-Pod subscription.  These labels
+are service-mesh dependent - for example, for an Istio ambient mesh this should be 
+{"istio.io/dataplane-mode": "ambient"}.  
 
 You can then use the relation data to build your authorization policies:
 ```