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If it's multi year license then check this info.
When you purchase a multi-year license, you receive a set of license files equal to the number of years your license is valid. For instance, a three-year license consists of three separate license files. When you activate a multi-year license, you import all of the license files during the same activation session. The Symantec Endpoint Protection Manager merges the separate license files into a single activated license that is valid for the purchased duration.
While not recommended, it is possible to activate fewer than the full complement of license files. In this case, the Symantec Endpoint Protection Manager merges the files and applies the duration of the license file that expires last. For instance, a three-year license that is activated with only the first two files indicates a duration of only two years. When the third file is activated at a later date, the full duration of the license is reported accurately as three years. In all cases, the number of seats remains consistent with the number of seats that you purchased.
Reference: http://www.symantec.com/docs/HOWTO55354
This article can be helpful for the reference: https://www-secure.symantec.com/connect/articles/sep-121-and-license-concept