Directory Backup Function OS X

TTP v 8.0.5
OSX 10.11.5

I'm trying to use TPP Directory Backup function (System Preferences Panel). I'm having two issues:
1) I mount an external drive, check the drive in the lest, and choose to Back up Now. The directory is backed up to a folder with the volume name. I can see the folder with content (i.e., 100MB). When I unmount the drive, the same folder that had hundreds of MB after the backup, now has 0MB. Why is the information deleted when the drive is not mounted? Doesn't this defeat the purpose of backing up the directory?

2) maybe related. I choose a location other than my system drive to save the directory back ups to. Regardless, all the backup are saved to the System Drive (Machine Library > Application Support > TechTool Protection). Why are the files not being saved in the assigned drive?

Please advise.
Thanks.