On Centralnic platform domains that have a configured price different than GA price are considered premium, even though the price may be lower than GA price. The only exception to this are promotions that are applied on top of a previously determined standard/premium price.
This is most common on grandfathered domains (domains that were registered prior to a GA price change and the Registry operator has decided to respect the previous price throughout the lifecycle of the domain).
The image below shows all of the possible configuration points for price. Should your domain be configured as anything other than GA price, it will be marked as Premium.