When an application releases an interface that is implemented by TCustomVariantType or one of its descendants, it automatically calls __Release. Typically, interfaced objects use the __Release method to decrement a reference count. When the reference count drops to zero, the object is automatically freed. 

TCustomVariantType implements its own version of the IInterface methods _AddRef and __Release that avoid this typical behavior. An application should have only a single instance of TCustomVariantType, and that instance should not be auto-freed when it is not in use. Thus, TCustomVariantType implements __Release so that it always returns –1. 

_AddRef 

_Release