My usual method is to meter the shadows, meter the highlights, workout the brightness range and then adjust development if the brightness range is above 5 stops.

For example, if the brightness range is 6 stops then I do N-1 development.

Question:
If I was to meter the shadows, meter the highlights and then make an exposure at the average of the two, what is actually happening. What I mean is, how will the tones be distributed.