Catalog of B2D folder log shows "Backup set may not contain any data"?

This backup set has already been cataloged.

This backup set may not contain any data.

 

The above 2 statements are seen hundreds of times in the log from a Catalog Job (actually Inventory and Catalog) run on my permanently attached 6tb disk storage device in BE2010 SP1a+.

Can anyone tell me what they actually mean and should I be concerned or not?

 

Thanks,