In a form I am creating I have the following table:

when I click the Date picker I get this:

here is the JS I am using:

$(document).ready(function () {
  
  $.getScript('http://server/Forms/js/moment.js');
  
  $('.cf-table-block').on('blur', 'input', sumtotal);
  $(document).on('click', '.form-del-field', sumtotal);
  
  function sumtotal() {
    var hour = 0;
    var rate = 0;
    var total = 0;
    var subtotal = 0;   
    $('.cf-table-block tbody tr').each(function () {
      hour = moment($(this).find('.hour input').val(), 'HHmm');
      rate = moment($(this).find('.rate input').val(), 'HHmm');
      subtotal = hour.diff(rate, 'hours', true);
      $(this).find('.total input').val(subtotal.toFixed(2));
      total += subtotal;
    });  
         
  }
  
  function parseNumber(n) { 
      var f = parseFloat(n); //Convert to float number. 
      return isNaN (f) ? 0 :f; //treat invalid input as 0; 
  } 

});

What am I doing wrong; How do I make the NaN not appear?