DataTable警告：table id = table - Ajax错误（datatable.net/tn/7）

Question

I am trying to make dynamic the data table in server side that I've found through the internet(for preference http://mbahcoding.com/tutorial/php/codeigniter/codeigniter-simple-server-side-datatable-example.html) because in this tutorial the table and the columns is fixed.

Controller

public function __construct()
    {
        parent::__construct();
    $this->load->model('CrudModel');
        $this->load->model('AccountModel');
    $this->load->model('customers_model','customers');
    }
public function ajax_list()
  {
    // $list = $this->customers->get_datatables();
    $list = $this->AccountModel->get_datatables('customers'); //my table name
    $data = array();
    $no = $_POST['start'];
    foreach ($list as $customers) {
      $no++;
      $row = array();
      $row[] = $no;
      $row[] = $customers->FirstName;
      $row[] = $customers->LastName;
      $row[] = $customers->phone;
      $row[] = $customers->address;
      $row[] = $customers->city;
      $row[] = $customers->country;

      $data[] = $row;
    }

    $output = array(
            "draw" => $_POST['draw'],
            "recordsTotal" => $this->customers->count_all(),
            "recordsFiltered" => $this->customers->count_filtered(),
            "data" => $data,
        );
    //output to json format
    echo json_encode($output);
  }

The question is where $this->customers->count_all() and count_filtered() come from?