Surface.Lock makes no sense at least to me

Question

I'm using Surface.Lock to get pixels of the back buffer to test for falling of my character. the problem no matter what size rectangle I request I get 800x600 and the resolution is 800x600x32. It makes no sense. I should get at least a million bytes but i get 480,000. No one on the net know the answer. I am merely lock the surface to determine the color pixel under the characters rectangle. How simple can it be? byte[800,600] = Surface.Lock() Please help i'm in dire need! thansk, nick