There are jumps between -20, -40 and -60 in the LU12-range, and plenty of -20s sprinkled in sequences of -01.
Did refurbished/repaired consoles get a new serial, or take up serials of recalled or exchanged boards?
AFAIK for PAL the "non-white Wii = 40+"-rule also applies.
For white Wiis, the...