IM Item site error: value cannot be converted to enumerated field

Trying to import items with Integration Manager.  Receiving the following error regarding the Item Site Display Option.  Error: Value "xx" cannot be converted to enumerated field 'Qtys/Sites.Site Display Options'.  I'm trying to assign the Site ID to each of the items, so I'm populating the field Site Display Options because that Rule is Use Source Field.  I'm not sure what to put in the Source field for this.  I'm also populating the Default Site ID field from the Use Source Field.  That doesn't seem to be an issue.