On a cam card, or part listing, you will see two figures for duration. One is called advertised duration, and the other is at .050-inch lift.
The problem with referring to the first duration number is that is usually isn't consistent with other companies advertised duration. Its merely used as a way to market and name camshafts. For example Crane measures their advertised duration at .004-inch valve lift, while COMP measures at .006-inch lift, making the Crane cam sound like it has a longer duration.
The standard measurement is at .050-inch lift, making it easier to compare make to make. If either of these two figures were to be left out of a technical description of the cam, it would be advertised.