A regular or non-unique attribute is one that can be on the same record multiple times. A unique attribute is one that is marked as 'only allow one per record' on the attribute itself within RE > Configuration > Attributes.  

In order to allow the same 'category' of an attribute with different descriptions to be added to a constituent record, you will need to make a selection of "Add new attribute" instead of "Update existing" for the 'non-unique attributes processing rules option.  

Because there can only be one 'unique attribute' per record, the only options are to "update existing" or "Ignore the new value".  

For more information regarding constituent and relationship attribute updates, please see the following area of our online user guide: http://omatic-importomatic.helpdocsonline.com/constituents