hapus data dengan codeigniter

mas/mbak saya mau tanya..

ketika saya membuat hapus data, yg kehapus kog mesti data yg idnya paling akhir, kenapa ya penyebabnya mas ?

source code model

function hapus($id){
    	$this->db->where('id',$id);
    	$this->db->delete('anggota');
    	return true;
	}

source code Controller

function hapus(){
		$id = $this->input->post('id');
	    $this->m_admin->hapus($id);
	    $this->session->set_flashdata('notif','<div class="alert alert-success" role="alert"> Data Berhasil dihapus <button type="button" class="close" data-dismiss="alert" aria-label="Close"><span aria-hidden="true">×</span></button></div>');
	    redirect('admin');
	}

source code VIew

 <div class="modal fade" id="delete_confirmation_modal" role="dialog" style="display: none;">
	    <div class="modal-dialog" style="margin-top: 260.5px;">
	                <div class="modal-content">
	            <div class="modal-header">
	                <button type="button" class="close" data-dismiss="modal">×</button>
	                <h4 class="modal-title">Do you really want to delete this Category? <?php echo $dt['id'];?></h4>
	            </div>
	            <form role="form" method="post"  id="delete_data" action="<?php echo base_url('admin/hapus')?>" >
	                <input type="hidden" id="delete_item_id" name="id" value="<?php echo $dt['id'];?>">
	                <div class="modal-footer">
	                    <button type="submit" class="btn btn-danger">Yes</button>
	                    <button type="button" class="btn btn-primary" data-dismiss="modal">No</button>
	                </div>
	            </form>
	        </div>

	    </div>
	</div>

source code javascript untuk hapus data

<script>
		$(document).ready(function()
		{
		    $("#hapus").click(function()
		    {
		        //Say - $('p').get(0).id - this delete item id
		        //modal.find('#delete_item_id').attr("value",div.data('#delete_item_id'));
		        $("#delete_item_id").val( $('p').get() );
		        $('#delete_confirmation_modal').modal('show');
		    });
		});
	</script>

Terimakasih