Dell battery S/N number ONLY 18 digits!!

Hi,

My cousin has a Dell Inspiron laptop. His battery recently failed as it refused to charge. He contacted Dell Support and they asked for the 20-digit serial number. But his battery ID had only 18 digits!!

Does this mean his battery is fake?

His battery Id is: 

KR-KY77-71766-1PK-S0RS-A00  (AFAIK last 3 digits are not part of S/N. So only 18 digits.)

DP/N KY77

The sticker says its made in Japan. The Dell part no. is generally 6 digits. He has only 4!!

Can anybody confirm is this a genuine or fake battery.

Thanks!