How do I make the form require a 10 digit phone number?

when you enter a phone number it keeps saying "Input should not be greater than the maximum value: 10"

thank you

I have checked your form and see that the number field is being used for Phone number. You may use the Phone number field instead of the number field in order to get the phone number.

If you want you may enable the Input Mask from the field properties to merge the Area code and phone number.

Hope this information helps!