No worries mate, your not thick. It has no real meaning. I've seen the BYE plate of a few powerful sports cars over the years with the BYE catching my eye. I like the plate because it looks clean and simple, the less letters and numbers the better in my eyes.
I first saw a very similar plate on a black twin turbo supra "K30BYE", I mentioned it to my partner and she bought me the one I'm selling.
It could mean you have enough power to leave another vehicle behind (lots on people liked it when I visted the Nurburgring last summer lol)
It could be a plate you just want people to remember, there is another 350Z in my town with K15BYE. People notice the plate and think its me, they dont read it just assume it was me lol.
Its like any private plate in the world, unless you understand or the reason behind the plate has been explained if there is one they mean nothing to passers by if you get me.
A lot of people buy them just to hide the age of there vehicle, if you didnt know anything about Z's people could think its a new vehicle.
Alex