KEDA - RabbitMQ autoscaler is slowing down when reaching few messages

Question

I'm using KEDA autoscaler with RabbitMQ.

When I queue 200 messages, KEDA is correctly using my 50 GCP nodes.

When it lasts less than 30 message in the queue, KEDA start scaling down, and it's only uses 15 nodes instead of 30...

My config:

  pollingInterval: 10
  successfulJobsHistoryLimit: 0
  failedJobsHistoryLimit: 1
  maxReplicaCount: 70
  triggers:
    - type: rabbitmq
      metadata:
        protocol: amqp
        queueName: main.quuee
        queueLength: "1"
      authenticationRef:
        name: keda-trigger-auth-rabbitmq-conn

How to make KEDA uses all the nodes available ?