SYSTEMBACK Query

[newtusmaximus]

First Time of use
  Want to be able to restore operating system and user files in the event of  sda failure. cf Windows full Backup/restore
 
0)  LL2.6 32bit = on HPdc7760  with 3 GB Ram  Dual core Intel CPU 1.9 GHZ
1) System internal  160 GB HDD  default single partition ( + swap etc) EXT4.  @  24.9 GB  Free = sda
2) Freshly formatted (Gparted) old External USB 2.0 160 GB HDD default single partition EXT4 @149 GB Free  = sdb1
No files/folders on SDB1 ( hidden or otherwise).
Ist System back up:aim  to be able to restore operating system and user files in the event of  sda failure  No previous restore points
Storage point path chosen /mnt/sdb1
Point Operations: Create New = 18:21 start  Creating Store Point stopped at 18:45  i.e approx 24 minutes to complete

Restore point appears  on systemback screen as 2016-01-07,18.20.59
Close SystemBack
SDA  now reads  only 14.5 GB Free
SDB now still reads 149.3 GB Free  NO file visible. ( incl hidden Files)
Please advise what is going on – what have I missed.
Also What is the difference between "SystemBack" and "Backup" in menu


  TKs