TIP: Alphabetic succession; a game starting mission setting similar to an American season.
Setting "15=" as the beginning of the code indicates that this season has a starting mission setting similar to an American season--
S15, where one team would be eliminated right after it.
Alphabetically sequence of the number:
15=O, 18=R, 2=B. Rearrange them and you get ROB. '+' in Chinese is pronounced as "Jia". Two "+" means "Jiajia."
Therefore the code means
Rob and Jiajia were eliminated right after the starting mission.