What's the defference between "new>PoItem" and "new>/PoItem" in data binding?

Hi experts,

    I'm confused about this question,What's the defference between "new>PoItem" and "new>/PoItem" in data binding?

    I create a model like this:

        var newModel = new sap.ui.model.json.JSONModel(sRootPath + "/model/mock.json");this.setModel(newModel, "new");

    When I do data binding,Sometimes "<Input type="Text" placeholder="{i18n>PoItem}" value="{new>/CompCode}" />" works,

    but sometimes "<Input type="Text" placeholder="{i18n>PoItem}" value="{new>CompCode}" />" works,why?