The numbering is not odd at all if you think about it. In the main retail line, every retool got a new number,
regardless of character, and apparently new accessories make them eligible as well. Compare:
MP-12 Lambor & MP-14 Alert
MP-17 Prowl, MP-18 Streak & MP-19 Smokescreen
MP-20 Wheeljack & MP-23 Exhaust
MP-22 Ultra Magnus & MP-31 Delta Magnus (new face plates and figurine)
And Starscream got two releases based on the same basic mold, yet got two numbers: MP-03 and MP-11.
The sub-numbering is a bit more random and probably impossible to figure out, but they have being more limited runs in common.
That said, can I say I called this one?