Serious issue with custom fields

I’m trying to put a custom field for phone numbers in my comments. To do this, I am going to

Forms>Edit Form>Add Field>Number

Unfortunately, the option to “Display in comments” for the custom field is staying permanently checked, regardless of what I do to uncheck it(even clearing cache). As a result, my commenters get their phone numbers prominently displayed alongside their comments, which is not the desired result. Please help me uncheck the “Display in comments” option.

The page I need help with: [log in to see the link]