It would be very unlogic to set a delay in a video setting while the videopicture is already late (7 frames or 280 ms).
Nuendo is not a typical video programm, while i monitor over a digital mixer to set the delay on audio while using finalcut pro to have sync video and audio I can tell that the audio is delayed and the video is unafected by the delay setting.
If it would affect only the video picture and not the audio the it would do exactly what i request and advance the video by the setting. I can tell you it does not do this!
Maybe it will convince you if you import a video with speech only (audio as well as video). Play this on screen (press f8) then set a vast delay in the top most video setting like 800 ms, then tell me what happened? The video is early or the sound is late? Well the sound is late, prove is connect a microphone and try record a dialogue sync to the picture, just speak along. (This just to test. On screen the video is pretty much sync without the delay setting, depends on the monitor you use. Typicaly a one frame offset is hard to see for a untrained eye)
Tell me the result!
It is not different for a black magic card.
Frank K