A new release is a new project which copies the same project settings as your current project but does not copy the status, notes or assigned users of any tasks. The intent of the "new release" function is to model the deltas between projects. For example, if you did not change the authentication component in a particular release, then you may not need to review the authentication tasks in that release. The "Changes since last release" section of the project settings only appears for new releases. By unchecking answers in this section, you can decrease the number of tasks, and therefore the amount of work required to secure the release.
Warning: Only uncheck a "Changes since last release" answer if you are certain there have been no changes. For example, uncheck "Changes to user output" only if you are certain that there will be no new web content on a web application. Unchecking answers incorrectly here may result in security tasks not appearing, potentially leading to decreased security in your application.
How to create a new release from the Project->Overview page
Changes since last release project settings