In an aws-ebs-csi-driver chart.yaml why is there an extra -0 in the kubeversion ? kubeVersion: ">=1.17.0-0"

In an aws-ebs-csi-driver chart.yaml why is therean an extra -0 in the kubeversion ?

for example..in any example chart I find it says for example ... kubeVersion: ">=1.17.0-0"

any help gratefully received