https://github.com/jenkinsci/jenkins/blob/f49b4b9418e0246463dd4e50bf9f3a076c3e488a/war/src/main/webapp/scripts/hudson-behavior.js#L828 compares min and max, which are strings.

"5" would be greater than "10" here, because they're compared by character, not numeric value.

To reproduce, compare form validation behavior of e.g.

<f:number min="10" max="20" clazz="positive-number-required" />

and

<f:number min="5" max="10" clazz="positive-number-required" />