if you have a field that is using `<f:number clazz="positive-number" min="1" step="1" />` you can submit a garbage number as far as java is concerned without any formvalidation warning.
so you can enter `e` `3e` or lots of this.
however Jenkins will then parse this usign standard java terms and well - `e` is not valid here, so you get a number format exception.
For example create a job and select "Discard old builds" and enter "e" as the "days to keep builds.
observe there are no formvalidation errors and save the form
reconfigure the job and not that the value is missing.