Parties are marked as nonduplicates of other parties as part of creating merge requests from System Duplicate Identification batches, or just updating duplicate sets in SDI batches. Nonduplicate mappings ensure that the parties are not selected as duplicate candidates in the future. See: System Duplicates.
For the selected party, only nonduplicates with an end date of today or later are displayed. To administer mappings, you can change the end date:
To make the mapped parties available to be selected as duplicates again.
To update the duration of the nonduplicate mapping.
So that the two parties to be always mapped as not duplicates of each other.
You can display certification levels and reasons through personalization. Certification assignments indicate the quality of records, and the meaning of each level is based on your organization's business needs. See: Assigning Certifications.