Subtract in PM and AM format in Sql Server 2008

Thank you in advance.

I'm going around trying to subtract PM from AM

The difference of format AM to PM the result is correct; however when rest of PM to AM the result is not the expected one

The insertion in the BD I do it this way:

public function insertarTiempo($usuario,$depto,$turno,$super,$jefe,$gerente,$area,$costo,$cantidad,$motivo,$status,$fecha,$fechaInicial,$fechaFinal)
{   


$idinserted = 0;



$week=  "" . date("W", strtotime($fecha));

$sql = "INSERT into tblHorasExtra VALUES('".$usuario."','".$depto."','".$turno."','".$super."','".$jefe."','".$gerente."','".$area."',".$costo.",'".$cantidad."','".$motivo."','".$status."',CONVERT(DATETIME, '".$fecha." 00:00:00', 103),0,0,0,'".$week."',CONVERT(DATETIME, '".$fechaInicial." 00:00:00', 103),CONVERT(DATETIME, '".$fechaFinal." 00:00:00', 103));  SELECT SCOPE_IDENTITY()";


//echo $sql;


$stmt = sqlsrv_query($this->conn,$sql);

    if( $stmt === false) {

        die( print_r( sqlsrv_errors(),true));
        echo " <br/>" . $sql;   
        $done = false;

    }else
    {
        $done = true;       
    }

    //Liberar memoria   
sqlsrv_next_result($stmt); 

sqlsrv_fetch($stmt); 

$idinserted =  sqlsrv_get_field($stmt, 0); 

    sqlsrv_free_stmt($stmt);    


    return  $idinserted;

}


Y la consulta de esta manera:

    public function mostrarDetalles($folio)
{

    $res = array();
    $i = 0;


    $stmt = sqlsrv_query( $this->conn,"SELECT t.idTiempo as folio,c.nombre + ' ' + c.apellidos as Supervisor,d.nombre + ' ' + d.apellidos as jefe ,f.nombre + ' ' + f.apellidos as gerente,ar.Descripcion as area,dp.Descripcion as depto,t.costo,t.cantidad,t.motivo,convert(nvarchar(30), t.fecha, 103) as fecha ,convert(nvarchar(30), t.fechaInicial, 103) as fechaInicial,convert(nvarchar(30), t.fechaFinal, 103) as fechaFinal,t.status,t.AprobSuper,t.AprobJefe,t.AprobGerente,t.idSuper,t.idJefe,t.idGerente,tu.Descripcion as turno,t.semana from tblHorasExtra t JOIN tblpersonal c on t.idsuper = c.idclave JOIN tblpersonal d on t.idJefe = d.idclave JOIN tblpersonal f ON t.idgerente = f.idclave JOIN tblArea ar ON t.idArea = ar.idArea JOIN tblDepto dp ON dp.idDepto = t.idDepto JOIN tblturno tu ON t.idTurno = tu.idTurno where idTiempo = ".$folio." order by folio desc");
//select CONVERT(varchar(15),CAST('17:30:00.0000000' AS TIME),100)

    if( $stmt === false) {

        echo $qry;
        die( print_r( sqlsrv_errors(), true) );

    }

    while( $row = sqlsrv_fetch_array( $stmt, SQLSRV_FETCH_ASSOC) ) {

        $res["folio"]  = $row['folio'];
        $res["Supervisor"]  = $row['Supervisor'];
        $res["jefe"]  = $row['jefe'];
        $res["Gerente"]  = $row['gerente'];
        $res["jefe"]  = $row['jefe'];
        $res["gerente"]  = $row['gerente'];
        $res["area"]  = $row['area'];
        $res["turno"]  = $row['turno'];
        $res["depto"]  = $row['depto'];
        $res["costo"]  = $row['costo'];
        $res["semana"]  = $row['semana'];
        $res["fechaInicial"]  = $row['fechaInicial'];
        $res["fechaFinal"]  = $row['fechaFinal'];
        $res["cantidad"]  = $row['cantidad'];
        $res["motivo"]  = $row['motivo'];
        $res["status"]  = $row['status'];

        $res["idSuper"]  = $row['idSuper']; 
        $res["idJefe"]  = $row['idJefe'];   
        $res["idGerente"]  = $row['idGerente']; 

        $res["fecha"]  = $row['fecha'];
        $res["AprobSuper"]  = $row['AprobSuper'];
        $res["AprobJefe"]  = $row['AprobJefe'];
        $res["AprobGerente"]  = $row['AprobGerente'];
    }

    sqlsrv_free_stmt($stmt);
    return $res;
}

And finally I do the subtraction to be able to show it in EXCEL

foreach ($empleados as $row) {

$datos = $db->consultarFecha($row['idemp'],$row['fecha']);


$objPHPExcel->setActiveSheetIndex(0)
        ->setCellValue('A' .$i, $row['idemp'])
        ->setCellValue('B'. $i, $row['Nombre'])
        ->setCellValue('C'. $i, $row['fecha'])
        ->setCellValue('D'. $i, $row['horas'])
        ->setCellValue('E'. $i, $row['area'])
        ->setCellValue('F'. $i, $detalles['depto'])
        ->setCellValue('G'. $i, $datos['fechaEntrada'])
        ->setCellValue('H'. $i, $datos['fechaSalida'])
        ->setCellValue('I'. $i, abs($datos['fechaEntrada']- $datos['fechaSalida'])); 

//Resta de Horas con valor absoluto, para no mostrar horas en negativo:  ->setCellValue('I'. $i, abs($datos['fechaEntrada']- $datos['fechaSalida'])); 
$i++;

}