A SingleUse class can only supply one instance of itself per copy of its component.
Assume that your COM component has two SingleUse object classes, ClassA and ClassB.
If two clients want to instantiate copies of ClassA from your server at the same time, ActiveX
runs a second instance of the server each time an instance of ClassA is created.
If one client wants to instantiate a copy of ClassA and another client wants
to instantiate a copy of ClassB, however, ActiveX will allow both of them to use
the same copy of your server, as long as each object instance is the first requested
instance for each class.