Back up file versions

Dear Sir, 

I have chosen the specific file back up mode and selected the files to be backed up. After that i have chosen the back up frequency to daily and i almost back up in every 2-3 days. I have also chosen to keep 20 versions of the file history. 
My issue is my software says data backed up succesfully. but when i go to the physical location in my passport , i could see only 1 set of back and the previous files cannot be seen. It appears that only one set of back up is been created and no previous versions of the files are being kept. Kindly help as i would like to keep the data back day wise. 
My system details are 
Winows 7 - 64bits 
i3 processor - 8 Gb Ram, WD Smartware version 2.2.1


The WD SmartWare backup solution will create additional copies using the file history option when the files themselves are modified. WD SmartWare will not add additional copies of files that remain unchanged as this option works individually per file as opposed to affecting the entire backup.