D600 Filename Sequence (and camera observations)

My D600 kit arrived a few weeks ago, and I just noticed that the filename sequence is in the upper 3,000s.  Looking back, my first picture was 3,687.  Is there a more optimistic explanation than the one I am suspicious of?

While I am here, my short term observations:

Good/Other:

• VERY high quality pictures with noticeable ISO and detail improvement over my D700 and D300s!  That's why I got it.  Low light wrestling pictures and limited focal length football pictures should both be improved.
  
• size and shape generally just fine
• U1 & U2
• Auto ISO is improved and now usable for me
• some control placement differences from previous cameras but perhaps more logical and I am getting used to them
• no 10 pin connecter, but I understand I can get a new inexpensive IR trigger
• my only project with the flash sync port was a failure so I don't miss it
  
• I haven't noticed any dust
  

Disappointments:

• I really miss my AF-on button, the reassigned AE-L button is OK but doesn't fall directly under my thumb
• I really miss the larger AF spread, I find myself having to focus and recompose almost all the time
  
• the Flash EV button is combined with the flash pop-up button so with external flash (on or off body) the camera flash pops up when changing EV
• with raw files the Auto WB seems warmer than previous cameras, I could often use the camera WB as imported into lighroom, but now I seem to be making more adjustments
• lower sync speed might be an issue outdoors
  

BP