Inked-on edge numbers, usually added to a workprint and mag track after syncing, so that corresponding sound and picture can always be properly aligned during editing. They are also used for the general organization of the footage. Sometimes the term edge numbers are used, and although this is not incorrect, care should be taken that it is understood that you are talking about the inked-on numbers and not the latent edge numbers

Glossary of Film Terms - http://homepage.newschool.edu/~schlemoj/film_courses/glossary_of_film_terms/
reprinted with permission