10.5.2 shows Darwin v5.xx.xxx???? Isnt it at Darwin 9 now

[mrburns05]

I was just reading a post, long story short - guy installed darwin 9, out of curiosity i rebooted to see my darwin version with zeph's 10.5.2. I have v5.x

Im confused as to why we wouldnt have darwin 9, and whether or not i can install it with reinstalling leo?

Thanks in advance for the help guys