3. Property

Now you can see the score. The players must get seven points to win. In Score.ss.xml, there is a stasc property tag:
<ss:property name="Numbers" target="textContent" order="0"/>
This does almost the same as stasc attribute but stasc property referes property of dom object instead of XML attribute. When order is specified, for example, "0" means the first parameter of the factory method. It is also the same as stasc attribute, although it was not used so far. So the scoring is done like:
Score(got + " - " + lost);

Attribute and Property

I'm afraid that you might be confused about difference between attribute and property. Their purposes are almost the same. Some of the properties are accessible as attributes. But some of the properties, e.g. textContent, can't be attributes. On the other hand, there are attributes not defined as properties. In case that both ways are possible, property may be better for performance.