The difference between default and $default in Survivorship Group

Question : 

What is the difference between default and $default within the entity 'appliedSurvivorshipGroup'?

Answer : 

• default This designation means that the attribute’s Operational Value (OV) was determined by using the entity type’s default survivorship group. The default survivorship group refers to the specific group whose JSON configuration includes the property "default": true. Typically, this group’s URI ends with /survivorshipGroups/default.
• $default This label indicates a different scenario where the engine was unable to locate any explicit survivorship rule for the attribute within the applied group. Moreover, it also did not find any corresponding rule within the entity’s default survivorship group. Because of this absence of specific rules, the system automatically reverted to the tenant-level “default strategy.” This tenant-level default strategy acts as a fallback mechanism, ensuring that the attribute’s Operation Value can still be computed even when no direct rules are defined at the group or entity level.