Portforwarding on Port 8000 for Ratel with Kubernetes

I wanted to deploy a Dgraph Single Server per Kubernetes. Thereby i used this documentation https://dgraph.io/docs/deploy/kubernetes/.

Portforwarding the Port 8080 works fine.

When i Portforward 8000 there comes an error.

And for my understanding i need the 8000 port for ratel. So what should i do that this port works?