I think JJP 'tries' to make the LE numbers unique. But I would guess mistakes happen because it really is just a number. The LE's are more about the maximum number built. But there are people that would like their LE numbers to match - or for a specific number that may have some sentimental value (or mean something to the theme).
For example: I bought my Hobbit from JJP - and they called to let me know my machine was about ready and did I want a specific LE number? I said, I would like 1932 because that is the year the hobbit was written and I though maybe it would make the pin more cool. But she said that number was already taken - so I just said any number is fine: I got 835 (which is fine). My hobbit is an SE (Smaug Edition) - So I would expect there could be an LE with number 835.
I think it is probably just a mistake - due to that WOZ number having some meaning. Heck, there may have been another that slipped through the cracks.