Don't work labels in alert

Hi people, I’m with a problem about labels in alert, I view a doc about “Labels in Grafana Alerting” but I was don’t understand how define “labels.cluster”. I’m monitoring a cluster k8s and have a labels cluster, I have a defined variable also and I choose my clusters. but in the summary showme , somebody know for something about.

Can you confirm: are you using the new Grafana Alerting platform (first released in Grafana 8) or the legacy alerting platform? I should note that the legacy platform is no longer actively developed:

yes, I am use a grafana v8.5.2 and the new approach using a contact points.