It's an old trick for compression/size limit competitions. You have N bytes allowed, but you can get an extra M bytes by putting them in the filename (minus however many bytes it takes to access the filename)
like if you several uncompressable (random) files you can "compress" them further by moving some of their bytes into the filenames.
But my best entry still does: http://wildmag.de/compo/Midcoast-The_Wormhole/5.htm