Pull processing is when a film is shot at a lower ISO speed than what’s listed on the box. When developing it, you tell the lab that you want pull processing and they change the development times to compensate for the change. In general, pull processing results in lower contrast and lower grain.
Pull processing is not as common as push processing because slower speed films are more readily available than high speed films, and film can be overexposed with great success, so it’s just not something that’s often needed. Also, color negative film doesn’t work as well with the process as it does with push processing, so it’s not very commonly done on color photos. Black and white negative film is much more forgiving to the process however and actually offers a unique lower contrast look when it’s done. So Film 06 includes pull processed presets on the two black and white films, Ilford HP5 and Kodak TRI-X 400.