Use this directory when you have a level you download online that you want to try out. Simply create a new text file with the next name in line, IE: 002.txt, 003.txt, 004.txt, etc. Then open the text file and copy and paste the map into the file. Then run the batch file "ASCIIpOrtal_extra_levels.bat" or at the main menu in the game choose the option "Change map set" and type in "extralevels". Then start the game with your custom levels.