One Panel #585: The Dimensions of Length, Width, and Thickness

From "Case of the Runaway Skyscrapers" by Jerry Siegel and John Sikela, Superman #16 (June 1942)

The villain is called Mister Sinister (should have taken out a trademark, DC) and he's a skyscraper thief from the Fourth Dimension. When Superman follows him through the dimensions, things get real "funhouse mirror" for him. Now will someone go back in time (through the ACTUAL Fourth Dimension) and tell Jerry Siegel the dimensions of length, width and thickness is where we ALREADY live?