How Kubernetes Horizontal Pod Autoscaler calculates CPU percentage?
To the horizontal pod autoscaler 100% of a metric (cpu or memory) is the amount set in resource requests. So if you pod requests 100m cpu, 9m is 9% and it would scale out on 75m.
Double check if you really have requested 1 (or 1000m) cpu by issuing kubectl describe pod <pod-name>.