This generates disk usage information. The disk usage information is designed to see what could be freed when removing older versions. Therefore, it will start with the most recent version, since you’ll want to keep this version in any case. This first size will be the size required to store one full backup (for the backup use case).

Then, older versions are examined. Only the sizes of the files are counted that need to be kept additionally to be able to retrieve the older version completely. Since most of the files will be unchanged when compared to the current version, the increments will usually be small.