.8 Why is that the finder version?

Currently on my mac.
System is 10.5.6
The finder is 10.5.8

How is the finder ahead of the system? How is that possible? And why would apple do this?

finder, like pretty much anything else, is just an application. while it's pretty much integral to your OS X experience, it is a distinct app from the OS. i'm actually a bit surprised the version numbers are so close.