ทำไมฟอร์มส่งค่าเลข3 หลักหรือ 2 หลักมาแค่ตัวเลขหลักหน้าหลักเดียวครับ

  $SEQ = null;
	
   if(isset($_GET["Asset_ID"]))
   {
	   $SEQ = $_GET["Asset_ID"];
	   
   }

   ?>
   

 <center>
 <p>&nbsp;</p>
 <p>แบบคอมพิวเตอร์ </p></p> 
 <form action="save_add_user_repair.php"   id="frmMain" name="frmMain" method="post">
  
    <table width="580" cellspacing="0" cellpadding="0" bordercolorlight="#CCCCCC" bordercolordark="#FFFFFF" id="myTable2">
     <!-- head table -->
     <thead>
       <tr>
         <td width="98" height="26" align="right">Number : </td>
         <td width="85" align="left"><input  name="Asset_ID" type="text"  id="Asset_ID" value="<?=$SEQ?>" size="3" readonly/> </td>

  $SEQ = null;
	
	if(isset($_POST["Asset_ID"]))
	{
		$SEQ = $_POST["Asset_ID"];
	}
   ?>
<?php
	ini_set('display_errors', 1);
	error_reporting(~0);
	error_reporting(0); 
	$serverName = "";
	$userName = "root";
	$userPassword = "";
	$dbName = "";

	$conn = mysqli_connect($serverName,$userName,$userPassword,$dbName);
	mysqli_set_charset($conn, "utf8");
	
	$User_name = $_REQUEST["User_name"];
	$Branch_ID = $_REQUEST["Branch_ID"];
	$Department_ID = $_REQUEST["Department_ID"];
	$Telephone = $_REQUEST["Telephone"];
	$Date_sent = $_REQUEST["Date_sent"];
	$SEQ = $SEQ["Asset_ID"];
	$Asset_re_detail = $_REQUEST["Asset_re_detail"];
	//$Date_finish = $_REQUEST["Date_finish"];
	
echo	$sql = "INSERT INTO user_repair(User_name, Branch_ID, Department_ID, Telephone, Date_sent, Asset_ID, Asset_re_detail, Date_finish)
			 VALUES('$User_name', '$Branch_ID', '$Department_ID', '$Telephone', '$Date_sent', '$SEQ', '$Asset_re_detail', '0000-00-00')";

	$result = mysqli_query($conn, $sql) or die (" ข้อมูลผิดพลาด Error in query: $sql " . mysqli_error());