How to get prototype to display at 100% without cutting off the pages to the left and right.

When I select 100% for display for the prototype, it cuts off the left and right of the screen. I can only get it to display at 82%. Not sure why this is happening. But it seems like the screens look too small when viewing in preview mode or when viewing via the prototype link in the browser. If I try to zoom in via the browser, it doesnt do anything.