Meaning of Security Level Attribute in Manufactured Item Definition?

Hi,
Please can someone enlighten me on what the attribute 'Security Level' does when creating a group. I cannot find anything in the docs. Also, by default, the description on the item is populated as:

### WARNING ###
Default CATRule associated to has been applied via OpeningID .
You may have to define a new CATRule on your PLM customization.

What considerations should I make regarding this message?
Many thanks