Hi!
This game has 1 DLC called "Monster Prom: Second Term" with separate achievements. They are more or less detailed in the official wiki here:
https://monster-prom.fandom.com/wiki/Monster_Prom_(Game)#Achievements
Basically all achievements with their title starting with "[Second Term]" belong to the DLC. Maybe we can get the same separation in here? If it had been decided to keep them here like they are now because of other updates then please disregard.
Thank you again for your amazing work