From what I understand the last digits that you are seeing refer to the bug fixes, etc.
There is also a good article on wikipedia: http://en.wikipedia.org/wiki/Linux_kernel
There should be some documentation that redhat puts out when you get their update as far as release notes that will tell you thekernel version they are including. Of course you can always type in the command "uname -a" this will give you the current kernel you are at. I did find the following link that might be helpful