Validation Rules on input field not working

I have text input field I want to add validation to. But when I click the Plus sign to select the type of validation, I get the notification shown. (it is not possible to insert elements based on your current selection. the field is for 10 digit phone numbers starting from 0 and I’ll like to add validation restricting number of digits entered to be 10 and not more. How do I go about this.

Since version 2.5.2 update, I no longer see the Green tick when I select a check box on the interface. in this screenshot, notice there is no check mark beside the REQUIRED Validation.