ZingChart in Ember.js not displaying watermark

I have an ember.js project in which I included a chart with zingchart. As the Buy Page states, you must always display the watermark when using the free version. However there is no watermark displayed and I connot find how to display one.

These are my renderOptions:

let _renderOptions = {
height: 400,
width: "100%",
events: {
    node_click: function (p) {
        console.log(p);
        Ember.$('tr').css('background-color', 'transparent');
        Ember.$('#' + p.scaletext + '-row').css('background-color', '#D29A52');
    }
},
data: {
    "type": "line",
    "series": [
        {
            "values": [2.55, 1.82, 1.36, 1.15, 1.20, 1.10, 0.95, 1.00, 1.20, 1.04], 'text': 'Einnahmen (in Mio €)'
        },
        {
            "values": [3.01, 2.62, 2.51, 1.75, 1.48, 1.48, 1.36, 1.56, 1.51, 1.37], 'text': 'Ausgaben (in Mio €)'
        }
    ],
    "scale-x": {
        "labels": [2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015],
        'item': {
            'font-size': '18'
        }
    },
    "scale-y": {
        'item': {
            'font-size': '16'
        }
    },
    "legend": {
        'background-color': 'transparent',
        'border-color': 'transparent',
        'margin-top': '55px',
        'margin-right': '50px',
        'item': {
            'font-size': '15'
        }
    },
},
defaults: {
    "palette": {
        "line": [
            ["#ffffff", "#C5914D", "#C5914D", "#C5914D"],
            ["#ffffff", "#856234", "#856234", "#856234"],
        ]
    },
    "graph": {
        "background-color": "transparent"
    }
}

};