Your Triple Play device will always scan through the directories to make sure it backs up all the pictures.
However, if the picture has been backed up it will not back it up a second time.
A quick check to make certain that the backup worked as intended would be to launch the Mo Disk App.
Then tap "View Backup Storage"
From the bottom of the page, you will see MO Disk and iPhone.
This will reveal the Albums structure and photos, videos, and contacts that have been backed up.