pageSize plugin in the wrong position of bbar

I used a bbar in a grid, I also add a pageSize plugin on it. This plugin code comes from here .

Code:

                        bbar: {
                                xtype: 'pagingtoolbar',
                                store: this.store,
                                displayInfo: true,
                                displayMsg: this.displayText,
                                plugins: new Ext.ux.grid.PageSize(), 
                               listeners: {
                                afterrender : function() {
                                        this.child('#refresh').hide();
                                        }
                                }                               
                        }

I expect the pageSize combobox to be put at the left side of bbar.

1.jpg

but the combobox is at the right side ><

2.jpg

Does anyone know what's wrong with this plugin?