This text should be autosized to 40px computed font size (16 * 800/320), since the float:left causes this to be a new cluster, and it is 800px wide.
Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.

This text should be autosized to 30px computed font-size (16 * 600/320), since its width:600px makes it wider than the lowest common ancestor of its enclosing cluster, hence it will itself become a cluster.
Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.

This text should be autosized to 20px computed font-size (16 * 400 / 320), since it's not an autosizing cluster itself and its parent element is the enclosing autosizing cluster which is 400px wide.
Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.