我没有在php中增加10以上数据库的最大值

<?php
$con=  mysql_connect("localhost","root","");
      $d=mysql_select_db("laabhaa_crm",$con);

    $result=mysql_query("SELECT MAX(LT_8690) 
FROM lead") or die(mysql_error());

 if($row=mysql_fetch_assoc($result))
 $a=$row['MAX(LT_8690)']+1;

  ?> 
  <input type="text" readonly="readonly" value="LT" style="width:16px;"/>/
                    <input name="LT_8690" type="text" value="<?php echo $a;?>" readonly="readonly" id="" style="width:60px;">

                </td>
            </tr>
<?php
$con=  mysql_connect("localhost","root","