When Maintain a log of seeds is checked, the NextSeed method of the CAmosSeedManager class places an entry in the seed log each time it is called.
Prior to Build 5141 of Amos 5, the file containing the seed log was not allowed to exceed 800 bytes in length. When it it reached that length, the file was halved in length, retaining the most recent entries. Beginning with Build 5141 of Amos 5, the file length is halved when it reaches 32000 bytes.
The location of the seed log file is different for different versions of windows. If you want to make a backup copy of the seed log file, you can use the PersistFile method of the CAmosSeedManager class to get its name and location.