When your site receives new online constituent registrations and the new records appear to match existing online or offline records, it is important to resolve any conflicts promptly. Resolution is particularly important before running data sync operations because these operations will skip some records when potential duplicates exist.
The algorithm used to determine potential matches involves a number of parameters that determine the weight to give to first name matches, last name matches, same cities, etc. By default, only records that score at least 54 points when compared against one another will be flagged as potential duplicates. (Contact support if you need to make changes to the points allocated or the default threshold.)
You can resolve potential duplicates in your Luminate Online database by marking the records as a match, marking them as not a match, or by merging two records into an online master. (Note that if you are running data sync in real-time, the Luminate Online database will fetch the complete offline record for a merge; if you are not running in real-time, the fields from the offline record may be incomplete.)