This comes from my book Capitals for Calligraphy. I've also kept the "inflated" (convex) version that accompanies it in the book.
Letters look like containers to me, which can be inflated or deflated with imaginary air. These Inflated Short Gothic letters are made by shortening regular Gothic letters [date] and sucking the air out of them, so they seem to collapse inward. The letters that don't completely enclose a white space just cave in on one side. You can see Deflated Gothic on April 13. It's taller than the one here.