Div Selector nth-child

Question

使用此功能，我没有正确代码的数量：请参阅附件。我无法理解为什么......

<script type="text/javascript"> 
    $(document).ready(function(){ 
        var $riepilogo = $('#riepilogo');
        var $btn_riepilogo = $('#btn-riepilogo');
        var parent_table; 
        var quantity; 
        var tot_quantity; 

        $btn_riepilogo.on('click',function(){ 
            tot_quantity=0; 

            $('table',$riepilogo).html('<tr><th>Prodotto</th><th>Quantit‌​&agrave; (tot: <span id="tot-quantity"></span>)</th></tr>'); 
            $('form input[type="text"]').each(function(){ 
                quantity = parseInt($(this).val());

                if(quantity > 0) {
                    tot_quantity+=quantity;
                    parent_table = $(this).parent().parent().parent();
                    $('table',$riepilogo).append('<tr><td>'+$('div:nth-child(2)',parent_table).text()+'</td><td>'+quantity+'</td></tr>');
                    $('#tot-quantity').html(tot_quantity);
                }
            });

            $riepilogo.slideDown('fast');

            return false;
        });
    });
</script>