Seat numbering

Hi, I am sure someone will be able to answer my wifes question for me. We were in the Delta Sky Club lounge on Friday night waiting to come home from Orlando when she asked me why the seat numbers start at 6. I told her I don't know but I know where I can find out. So why do they start at 6 and not 1 ?.

I think there's a thread here somewhere that explains it, but I think it was down to the fact that originally some UC seats were upstairs on the 747, and they were numbered 1-5.

Edited to add: this thread contains HL's explanation.

When VS operated the 2 class A330 from MAN to MCO I was on the very front row of the Aircraft in PE, I'm pretty sure it started row 18 or something similar!

Thanks pjs for the link to HLs explanation, I knew someone would know, I will show my wife the link. Thanks once again.