A shooting script is the version of a screenplay used during the production of a film or video.
The numbers provide a convenient way for the various production departments to reference individual scenes.
This avoids having to print and distribute an entirely new draft for every set of revisions, which would entail crew members having to transfer all their handwritten notes to a new script.
In some cases, usually before the start of principal photography, an entirely new "white draft" will be distributed in lieu of colored revision pages.
The pages in a white draft are renumbered from scratch, while the original scene numbers are maintained.
When revisions are made to a shooting script, they must be accomplished in a way that does not disturb the pre-existing scene numbers.
This effectively retires the number so that it cannot be reused by a new scene inserted later at the same location.
Most screenwriting software applications include functions for handling the formats and procedures described above, with varying degrees of automation.