To make rules in a list work, you need apply the list to your form field.
On Gravity Forms form edit screen, click the arrow to open field options.
Then click "Advanced" tab.
Check Apply list check box in Custom Validation section.
And select the list you'd like to apply.
Now, if the field value is not a valid phone number then it will show error message in front when submit form.
Length isn't right:
Must be numeric:
First number must not be 0 or 1
Purchase Gravity Forms Custom Validation Pro