Hanging Punctuation is a way of typesetting punctuation marks and bullet points, most commonly quotation marks and hyphens, so that they do not disrupt the "flow" of a body of text or "break" the margin of alignment. It is so called because the punctuation appears to ‘hang’ in the margin of the text, and is not incorporated into the block or column of text. It is commonly used when text is fully justified.

When you pass this option, the bounds are computed by ignoring the standard punctuation from the text.