The function returns the picture instance number. If the parameter bPhysical is not defined or its value is False, the function returns the such the instance number that was required on opening the picture.
If the parameter is True, the function return returns the current picture instance number. The current instance number can be differ from the required number if the picture is opened as a subpicture and the parameter Multiple open of the connection is checked. 

If the function is called in the context of a Unit event, it returns an event not a Unit instance.