The NAN-BON counter is used to count objects that are long and cylindrical in shape, but it is also used to count some items that might not seem to be long or cylindrical, such as video cassettes, teeth, and numbers of flights.
(Video cassettes) Some people say that video cassettes are counted using the NAN-BON counter because the video tape inside is long, but others say it is because movies are counted the same way.
(Movies) The NAN-BON counter is used for movies since motion-picture films are long. When you talk about movies as a piece of work/production, you can use the SAKU/SAKUHIN counter as ISSAKU, NI-SAKU, SAN-SAKU. But the NAN-BON counter is more common to use.