Dynamic table with CSS Serial numbers

HTML

<link rel="stylesheet" href="https://code.jquery.com/ui/1.11.4/themes/smoothness/jquery-ui.css">
<script src="https://code.jquery.com/jquery-2.1.1.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.2.0/js/bootstrap.min.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.4/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://code.jquery.com/jquery-2.1.1.min.js"></script>
<div class="panel panel-primary">
  <!-- Development and Action Plan Review -->
  <div class="panel-heading">
    <h4>Table</h4>
  </div>
  <div class="bs-example">
    <div class="Container">
      <table class="table table-hover small-text" id="tb2">
        <tr class="tr-header">
          <th>S.No</th>
          <th>Name</th>
          <th>Age</th>
          <th>Class</th>
          <th>Year</th>
          <th><a href="javascript:void(0);" style="font-size:18px;width:33%;" id="addMore2" title="Add More Person"><span class="glyphicon glyphicon-plus"></span></a></th>
        </tr>
        <tr id="1A">
        <td><input type="text" name="SNo[]" readonly class="form-control"></td>
          <td>
            <input type="text" name="Summary[]" class="form-control">
          </td>
          <td>
            <input type="text" name="Action[]" class="form-control">
          </td>
          <td>
            <input type="text" name="Variance[]" class="form-control">
          </td>
          <td>
            <input type="text" name="PerformanceGap[]" class="form-control">
          </td>
          <td><a href='javascript:void(0);' class='remove'><span class='glyphicon glyphicon-remove'></span></a></td>
        </tr>
      </table>
    </div>
  </div>
</div>

CSS

#tb2 input[readonly]{
  background: transparent;
  border: none;
  box-shadow: none;
  width: 50px;
}

JavaScript

$(function(){
		$('#addMore2').on('click', function() {
				var data = $("#tb2 tr:eq(1)").clone(true).appendTo("#tb2");
				data.find("input").val('');
        numberRows();
		});
		$(document).on('click', '.remove', function() {
			var trIndex = $(this).closest("tr").index();
				if(trIndex>1) {
				$(this).closest("tr").remove();
			} else {
				
			}
      numberRows();
		});
    function numberRows(){
      $("#tb2 tr").each(function(){
      	$(this).find("td:first-child input").val($("#tb2 tr").index(this));
      });    
    }    
    numberRows();
	});