__Release implements the IInterface or IUnknown method that is called when an application releases a reference to this node's interface pointer. __Release decrements the RefCount property. In addition, it also decrements the reference count for the owning document, which it incremented when the _AddRef method was called. 

When __Release causes the node's reference count to drop to zero, __Release causes the node to free itself. 

_AddRef 

OwnerDocument 

System::TInterfacedObject::RefCount