Here are the major points that I took away from Kimball's piece, all of which are mentioned early on in the text and continue throughout.
1) Portfolios should be reflective in the sense that they should depict challenges you face, how you overcame them, and what you ultimately learned from each submission.
2) The standards of your work should somehow be explained and how you fulfilled those standards should be evident in your work.
3) You must present the portfolio in a way that will make sense and enables the audience to draw conclusions from it. You must create the portfolio with audience in mind.