saas-platform/frontend/saas-web/app/view/home/HomeController.js

Ext.define('saas.view.home.HomeController', {
    extend: 'Ext.app.ViewController',
    alias: 'controller.home',

    onSeriesTooltipRender: function (tooltip, record, item) {
        tooltip.setHtml(record.get('os') + ': ' + record.get('data1') + '%');
    }
});