Hey it's me
Dracula
Basically, the pointfile is a line made up of many dots that will show you where your leak is. The line starts approximately at the entity listed by the compile tools as being near the leak. It does not end anywhere specific, however it will at some point pass through the hole in the map. The best thing to do is follow the line and watch to see where it goes through a hole in the wall and ends up outside in the void. To follow the line most effectively, turn noclip on through the console command "noclip" allowing you to freely move in all directions. If it does nothing, do "sv_cheats 1" and "noclip" again. You may need to restart the map if the cheats parameter doesn't work.
If the pointfile ends before exiting into the void of the map, you may need to change the amount of particles the engine is using. A message saying "not enough particles" will be displayed when you type pointfile if this may be a problem. Add "-particles 10000" to the commandline used to run HL to gain more particles and extend the length of the line.