chapter 1 ，a description of float is not much accurate

[decadef20]

Floats are aligned to either the left or right outer edge of their container.

I was confused about the words 'outer edge their container'.A container should be a box which usually has padding and border.That's to say,the words 'outer edge their container' mean the left or right border of container.But it is definitely wrong. Here the spec says:

A floated box is shifted to the left or right until its outer edge touches the containing block edge or the outer edge of another float.

From my perspective, replacing container with containing block might be better. Thanks.