I sent an email to canon and they replied:
Thank you for contacting Canon product support regarding the file
numbers on your new EOS 60D. We value you as a Canon customer and
appreciate the opportunity to assist you.
If the card was used in the camera at all before it was formatted, and
it had been used in a previous Canon camera before this, there is a
chance that the camera simply picked up the file number from the card
itself. However, if this was a new card, or if it was formatted before
it ever touched the camera, then you may have a good reason to suspect
that the camera has been out of the box at least once before for a test
shot or some other use. If this is the case, you may want to contact
the dealer for further clarification. I sincerely apologize for any
inconvenience this may cause.
Please let us know if we can be of any further assistance with your EOS
Thank you for choosing Canon.