On the listing page, the filter for the number slider only shows a minimum value of 3, and a maximum value of 4. The settings in the backend are set to a min of 1 and a max of 30, and the actual listings themselves have between 1-20 for this attribute.
This data in the slider is based on the data in the listing. The restrictions that you specify in the attribute settings apply only to the input fields (when editing a listing).