At levels 50 and 51, players in a party gain abnormal(ly low) dungeon exp.
All members of the party will be affected regardless of their levels so long as a level 50 or 51 are present in the party.
Examples:
Solo:
While in party with a level 50/51:
(Oops lost rest of bad exp images, but that's the exp from the same mob that was supposed to be giving 6304)