ext分页问题

js是这样的//页面数据数量
    var pageSize = 2;
    
     var fields =
        [{ name: "prodTypeoid" },
            { name: "prodTypeName" },       //名称
            {name: "proDesc" }    //备注
        ];
//存储数据Store定义
    var store = new Ext.data.Store( {
     proxy: new Ext.data.HttpProxy(
                {
                    url: url
                }),
              //JsonReader固定格式
                reader: new Ext.data.JsonReader(
                   {
                    fields: fields,
                       root: "root",
                       //id: "prodTypeoid",
                       totalPorperty: "totalProperty"
                   })
});  var sm = new Ext.grid.CheckboxSelectionModel(
           { dataIndex: "prodTypeoid" }
       );
var cm = new Ext.grid.ColumnModel([
            new Ext.grid.RowNumberer({ header: "", width: 20, sortable: true }),
            sm,
  {header : '类别名称',dataIndex : 'prodTypeName'}, 
  {header : '类别描述',dataIndex : 'proDesc'}
]
);
cm.defaultSortable = true;
var pagingBar = new Ext.PagingToolbar
        ({
            store: store,
            pageSize: pageSize,
            //显示右下角信息
            displayInfo: true,
            displayMsg: '当前记录 {0} -- {1} 条 共 {2} 条记录',
            //displayMsg: '显示第【<b><font color=red>{0}</font></b>】条至第【<b><font color=red>{1}</font></b>】条 / 共【<b><font color=red>{2}</font></b>】条记录',
            emptyMsg: "没有数据显示",
            prevText: "上一页",
            nextText: "下一页",
            refreshText: "刷新",
            lastText: "最后页",
            firstText: "第一页",
            beforePageText: "当前页",
            afterPageText: "共{0}页"
        });
var DoQuerry = function () {
            store.reload({ params: { start: 0, limit: pageSize} }); //reload 参数：start 0 limit pageSize 18
};
//-------------------------------------------------定义列表Grid
        var grid = new Ext.grid.GridPanel
        ({
            id: "GridPanel",                                //GridPanelID
            layout: "fit",                                      //填充整个容器
            frame: true,                                        //True表示为面板的边框外框可自定义的，false表示为边框可1px的点线（默认为false）。
            border: true,                                       //True表示为显示出面板body元素的边框，false则隐藏（缺省为true），默认下，边框是一套2px宽的内边框，但可在bodyBorder中进一步设置
            stripeRows: true,
            height: document.documentElement.clientHeight ,    //- 15
            autoScroll: true,                                    //自动滚动条
            width: Ext.get("grid").getWidth(),                   //设置grid Ui forceFit 固定列宽             
            loadMask: { msg: '系统正在查询，请稍候......' },        //指定查询等待语句
            store: store,                                       //数据源
            sm: sm,                                             //SelectMode 选择模式
            cm: cm,                                             //colMode    列模式
            viewConfig: { forceFit: true },                     
            header: false,                                      //不显示title
            renderTo: "grid",                                    
            tbar: [                                              //toolbar标签
            new Ext.Toolbar.TextItem('类别名称(模糊查询)：'), 
            new Ext.form.Field({
                width: 100,
                id: 'lbmc_txt'
            }),                
            "-",                                                
            {id: "btnQuerry",                                   //刷新按钮
            text: "刷新",
            iconCls: "refreshicon",
            handler: DoQuerry
            }
        ],
        bbar: pagingBar,                                    //bottombar            
        listeners: {
            //grid内的右键事件 全屏蔽
            'contextmenu': function (e) {
                e.stopEvent();
                rightClick_Menu.showAt(e.getXY());
            },
            //表格行上的右键事件，在查询没有的数据的时候不能触发 
            "rowcontextmenu": function (grid, rowIndex, e) {
                e.stopEvent();
                
                //判断右键菜单项是否可用
                var r = Ext.getCmp("GridPanel").getSelectionModel().getSelections();
                if (r.length > 0) {
                    rightClickRow_Menu.items.get('editData_Mn').enable();
                    rightClickRow_Menu.items.get('deleteData_Mn').enable();
                } else {
                    rightClickRow_Menu.items.get('editData_Mn').disable();
                    rightClickRow_Menu.items.get('deleteData_Mn').disable();
                }                rightClickRow_Menu.showAt(e.getXY());
            },
            //行单击事件            
            "rowclick": function (grid, rowIndex, e) {
                               
            }
        }
    });
json字符串
{totalProperty:3,root:[{"proDesc":"测试","prodTypeName":"测试","prodTypeoid":"1"},{"proDesc":"测试","prodTypeName":"测试","prodTypeoid":"2"}]}
显示的时候只显示两条记录
当前记录 1 -- 2 条 共 2 条记录 
什么原因，求解决