There are 2 rule settings that determine how to choose fields (differently than your master) for field value selections based on your specific business needs.
Default Field Values – Define the general rule you want to use when determining the field value selections for the final record.
Specific Field Values – Set rules for specific fields on the object. These rules will supersede any settings in your default field or your master rule.
For more information on how to configure your field level rules, please visit our Merge Automation Rule page.