Newbie Vegas question...

My project is set to 8-bit.

However the Preview window shows Project, Preview, and Display at 1920x1080x32... which I'm assuming means 32-bit.

Preview Quality is set to Preview Full and the Project's Full Resolution Render Quality is set to Best. But it makes no difference what I set these to. The Preview window always shows 1920x1080x32. :-
What gives?

Thanks,
Jim