Actually it's much like the Linux kernel version vs the package distribution name and version.
I picked up Solaris at the 2.5 distro. From there it went to Solaris 2.5.1, 2.6 and then Solaris 7, 8, 9 and now 10. Sun just dropped the '2.' from the version, maybe for more cred
The kernel vesion is SunOS 5.x. So you're using SunOS kernel 5.8 on Solaris package distribution 8 or Solaris 8. Some people still stick the "2." in front of the name.
It's like the linux distros. The kernel is 2.4.21-47.0.1 but the Linux distribution is Red Hat 3.2.3-56.
Carl