If there is a significant bug fix or security update distros will usually back port those fixes to the current kernel they are using, then issue a 'update'. It's easier on end users this way.
So that may be part of the confusion.
If you want to know more for certain when was the last time you updated your kernel do a 'ls -l /boot/' and see the time stamps on the files there. (unless you've been playing around with them or something that would cause the time stamps to update.)
Also check out your boot menu configuration time stamp and contents in /boot/grub (if your using grup, or /etc/lilo.conf if your using lilo).
That should help. Also your modules in /lib/modules should shed some light on the subject.
Keep in mind that of course after a kernel update you have to reboot to make the changes go into effect.
