Phpspreadsheet/Codeigniter Undefined offset: 13

Good day I encountered an error which is called Undefined offset: 13 when I imported a excel file I get and error which is called undefined offset. May aim here is to import excel file.

My Controller

 public function import_teen()
      {
        $upload_file=$_FILES['upload_file']['name'];
        $extension=pathinfo($upload_file,PATHINFO_EXTENSION);
        if($extension=='csv')
        {
          $reader= new \PhpOffice\PhpSpreadsheet\Reader\Csv();
        } else if($extension=='xls')
        {
          $reader= new \PhpOffice\PhpSpreadsheet\Reader\Xls();
        } else
        {
          $reader= new \PhpOffice\PhpSpreadsheet\Reader\Xlsx();
        }
        $spreadsheet=$reader->load($_FILES['upload_file']['tmp_name']);
        $sheetdata=$spreadsheet->getActiveSheet()->toArray();
        $sheetcount=count($sheetdata);

This is the Array of Data

if($sheetcount>1)
            {
              $data=array();
              for ($i=1; $i < $sheetcount; $i++) { 
                $dor=date('y-m-d',strtotime($sheetdata[$i][1]));
                $lastname=$sheetdata[$i][2];
                $firstname=$sheetdata[$i][3];
                $middlename=$sheetdata[$i][4];
                $zone=$sheetdata[$i][5];
                $bday=date('y-m-d',strtotime($sheetdata[$i][6]));
                $age=$sheetdata[$i][7];
                $servicegive=$sheetdata[$i][8];
                $lmp=date('y-m-d',strtotime($sheetdata[$i][9]));
                $edc=$sheetdata[$i][10];
                $gpa=$sheetdata[$i][11];
                $remarks=$sheetdata[$i][12];
                $teenagepregnancy=$sheetdata[$i][13];
        
                $data[]=array(
                  'dor'=>$dor,
                  'lastname'=>$lastname,
                  'firstname'=>$firstname,
                  'middlename'=>$middlename,
                  'zone'=>$zone,
                  'age'=>$age,
                  'servicegive'=>$servicegive,
                  'lmp'=>$lmp,
                  'edc'=>$edc,
                  'gpa'=>$gpa,
                  'remarks'=>$remarks,
                  'teenagepregnancy'=>$teenagepregnancy,
             
                 
                );
              }
          $inserdata=$this->m->insert_batch_teen($data);

This code here is after the data is inputted it will redirect to the view

 if($inserdata)
          {
            $this->session->set_flashdata('message','<div class="alert alert-success">Successfully Added.</div>');
            redirect('dashboard/importteen');
          } else {
            $this->session->set_flashdata('message','<div class="alert alert-danger">Data Not uploaded. Please Try Again.</div>');
            redirect('dashboard/importteen');
          }
        }
      }

My Model

public function insert_batch_teen($data)
    {
      $this->db->insert_batch('tbl_teenage',$data);
      if($this->db->affected_rows()>0)
      {
        return 1;
      }
      else{
        return 0;
      }
    }