GHOST backup

In the push-to-GHOST help that “once a new backup, the original backup will be covered,” but I tried not long ago, for the first time the backup image file for 1.77G, made a back-up for the second time after 2.83 G, I delete the results of the third and then made a backup, only this time 1.88G.If you want to make that back up again, it is best to back up the original image file for later delete the backup.
Why I can not find The previous backup files Nam?
Restore regular backup of your hard disk (think of books) do great harm?
Please help me to explain, ha, thank you!

back up the injury in fact, but if so often to repair damage may be hard to argue, of course, is too often to the ghost can be seen on the hard drive ..
hurt, of course, is Some