menampilkan jumlah sisa selalu error dan tidak tampil...

Assalamualaikum Warahmatullahi Wabarakatuh...
 
Mastah2 yg saya hormati,
maaf sy sedang ada kesulitan membuat tampilan keterangan sisa dari script dibawah ini...mohon bantuannya mastah2...terima kasih sebelumnya
 
<?php
	include("sess_check.php");
	include("koneksi.php");
 
	$id=$sess_pegawaiid;
 
 
	$sql_g = "SELECT * FROM employee WHERE npp='$id'";
	$ress_g = mysqli_query($conn, $sql_g);
	$res = mysqli_fetch_array($ress_g);
 
	$sqlb = "SELECT * FROM cuti WHERE npp='$id' AND stt_cuti!='Rejected'";
	$ressb = mysqli_query($conn, $sqlb);
	$b = mysqli_num_rows($ressb);
 
	$sqlc = "SELECT * FROM cuti WHERE npp='$id' AND stt_cuti='Rejected'";
	$ressc = mysqli_query($conn, $sqlc);
	$c = mysqli_num_rows($ressc);
 
	$sqla = "SELECT * FROM cuti WHERE npp='$id' AND hrd_app=1";
	$ressa = mysqli_query($conn, $sqla);
	$a = mysqli_num_rows($ressa);
 
	$sqld = "SELECT jml_cuti FROM cuti WHERE jml_cuti=$jml AND hrd_app=1";
	$ressd = mysqli_query($conn, $sqld);
	$d = mysqli_num_rows($ressd);
 
 
	// deskripsi halaman
	$pagedesc = "Beranda";
	include("layout_top.php");
	include("dist/function/format_rupiah.php");
?>
<!-- top of file -->
		<!-- Page Content -->
		<div id="page-wrapper">
            <div class="container-fluid">
				<div class="row">
					<div class="col-lg-12">
						<form class="form-horizontal">
							<div class="panel panel-default">
								<div class="panel-body">
								<h2 align="center">Selamat Datang, <?php echo $res['nama_emp'];?>!</h2>
								<hr/>
								<center><img src="../foto/<?php echo $res['foto_emp']?>" width="120px"></center>
								<hr/>
								</div>
							</div><!-- /.panel -->
						</form>
					</div><!-- /.col-lg-12 -->
				</div><!-- /.row -->
 
				<div class="row">
					<div class="col-lg-4 col-md-4">
						<div class="panel panel-primary">
							<div class="panel-heading">
								<div class="row">
									<div class="col-xs-3">
										<i class="fa fa-check-circle fa-3x"></i>
									</div>
									<div class="col-xs-9 text-right">
										<div class="huge"><?php echo $a; ?></div>
										<div><h4>Approved</h4></div>
									</div>
								</div>
							</div>
							<a href="cuti_app.php">
								<div class="panel-footer">
									<span class="pull-left">Lihat Rincian</span>
									<span class="pull-right"><i class="fa fa-arrow-circle-right"></i></span>
									<div class="clearfix"></div>
								</div>
							</a>
						</div>
					</div><!-- /.panel-green -->
 
					<div class="col-lg-4 col-md-4">
						<div class="panel panel-yellow">
							<div class="panel-heading">
								<div class="row">
									<div class="col-xs-3">
										<i class="fa fa-plus-circle fa-3x"></i>
									</div>
									<div class="col-xs-9 text-right">
										<div class="huge"><?php echo $b; ?></div>
										<div><h4>Menunggu Approval</h4></div>
									</div>
								</div>
							</div>
							<a href="cuti_waitapp.php">
								<div class="panel-footer">
									<span class="pull-left">Lihat Rincian</span>
									<span class="pull-right"><i class="fa fa-arrow-circle-right"></i></span>
									<div class="clearfix"></div>
								</div>
							</a>
						</div>
					</div><!-- /.panel-green -->
 
					<div class="col-lg-4 col-md-4">
						<div class="panel panel-red">
							<div class="panel-heading">
								<div class="row">
									<div class="col-xs-3">
										<i class="fa fa-minus-circle fa-3x"></i>
									</div>
									<div class="col-xs-9 text-right">
										<div class="huge"><?php echo $c; ?></div>
										<div><h4>Rejected</h4></div>
									</div>
								</div>
							</div>
							<a href="cuti_reject.php">
								<div class="panel-footer">
									<span class="pull-left">Lihat Rincian</span>
									<span class="pull-right"><i class="fa fa-arrow-circle-right"></i></span>
									<div class="clearfix"></div>
								</div>
							</a>
						</div>
					</div><!-- /.panel-green -->
 
					<div class="col-lg-12 col-md-12">
						<div class="panel panel-orange">
							<div class="panel-heading">
								<div class="row">
									<div class="col-xs-3">
										<i class="fa fa-paperclip fa-3x"></i>
									</div>
									<div class="col-xs-9 text-right">
										<div class="huge"><?php echo $d-$a; ?></div>
										<div><h4>Sisa Cuti</h4></div>
									</div>
								</div>
							</div>
							<a href="cuti_reject.php">
								<div class="panel-footer">
									<span class="pull-left">Lihat Rincian</span>
									<span class="pull-right"><i class="fa fa-arrow-circle-right"></i></span>
									<div class="clearfix"></div>
								</div>
							</a>
						</div>
					</div><!-- /.panel-green -->
 
				</div><!-- /.row -->
 
			</div><!-- /.container-fluid -->
        </div><!-- /#page-wrapper -->
<!-- bottom of file -->
<?php
	include("layout_bottom.php");
?>