What does the duration present under the audience segments mean?
The duration showing up under the audience segments is the cookie duration (1 - 120 days). Cookie duration is the amount of time a user remains in a particular segment.
Each time a user visits your website, they will be tracked under a defined audience segment and a cookie will be dropped in their browser which will help us serve the ads.
Post the set duration, the user will be removed, and will be counted again only if they come back to the website.
To learn more, check out Audience Duration.