Ghost 15 are the numbers wrong?

I just noticed this the other day. I am running Windows 7 Pro and as I said Ghost 15.  According to the backup, Ghost copied +/- 25 gigabytes from the C drive to my F drive.  I think that number is about correct.  However according to the C drive properties there is +/- 40 gigabytes of used disk space on drive C.  I checked my data storage drive and compared it to the backup and they are just about the same.

 

I did have a virus attack the computer the other week and I did a restore the computer.  Could I be running two identical C drives but it only shows one?

 

Can someone explain why the backup is 27 gigabytes and the C drive says there is 41 gigabytes of used space on the drive.

 

Thanks for your help.

 

Jack