The idea is for numerical fields to, instead of using a conventional constraint on this field (that is only validated when the data is submitted), directly restrict the entry of data into this field, especially for the spinner appearance (let's call it "restricted spinner" appearance). E g. an integer that is constrained to values between 0 and 50. When these limits are reached the spinner buttons just stop adding (plus button at 50) or subtracting (minus button at 0). This would be a much more direct user experience.
