Very different snapshot sizes

I've been trying out System Backup 2010 (and some of the advanced utilities that come with it.) The first backup of my system was about 30GB. I then moved that out of the way (just for testing) and requested a snapshot of the system, and that too was about 30GB. I then made another snapshot, and surprised to find that the new one was about 16 GB. I browsed the contents of both, and they both had the same number of folders in the top level of the drive. Subsequent snapshots made with the Backup Wizard (of the whole disk) were also about 16GB.

What could explain the snapshot size difference? I have tried restoring my system to one of the smaller ones and the system worked fine. I did not act like I had lost half of the files, so presumably there was nothing critical in the other 14GB the early snapshots had. I know some versions of the Paragon software have the ability to do differential (incremental) backups but I do not see an option for that (and certainly did not intentionally select one) and also it is hard to imagine that 16GB would be needed to for a differential backup made so soon after a full backup.

 

System Backup doesn't create full snapshot each time.
It creates first full snapshot and all future automatic snapshots contain only changes which allows to save free space and time. When limit of snapshots to keep is reached, system backup merges full snap with older snapshots and continues the process .
All snapshots are workable.

 

Thanks for the reply! I do understand that the automatic backups keep one full backup and store just changes for the subsequent ones. I still have a few questions, though:

1) How could two backups, made a few minutes apart, result in the second file being 16GB in size? (Could there really be 16GB of differences?)

2) What happens if I go into System Backup, view the snapshots, and delete the first one? Will that also render unusable the subsequent backups that are differences? What if I delete a difference snapshot in the middle of a set?

3) Does the Backup Wizard (which I've mostly been using) also create differential snapshots, or does that one create full backups?

Thanks,
-Notralph