It could be based on the number of total accounts?  No idea, since my oldest is 6.5, and average is 5 and I'm pretty sure it gave me a 3 as well

Current: EQ FICO 664, TU FICO 683, EX FICO 698 | Starting Score: 525 (05/2012) Starting total revolving credit: $1100 | Current total revolving credit: $7000 Inquiries (12 Months): EQ 3 TU 2 EX 2 | Most Recent: 1/8/2013

2013 Goals: New Car 700 Club AMEX Member

AMEX Gold NPSL DCU Visa $2000 Cap1 Cash Rewards $2000 BOA Platinum $600 WalMart $800