To find out which workload type the pods are part of issue the following command:
kubectl describe pod o3db-0 -n project-c13 | grep -i controlled
You will get:
Controlled By: StatefulSet/o3db
We now know it is a StatefulSet workload type, so we can scale it as follows:
kubectl scale statefulset o3db -n project-c13 --replicas=1