Yes K92 would be later than K20 (K99 would be the last script to be executed) and K is for 'Kill'.
If I remember correctly with Sys V style scripts on Debian-based systems you are supposed to use update-rc.d to manage your startup scripts
. But yes, the basic idea is that the script will go under /etc/init.d and you will have symlinks pointing to it from directories (/etc/rc?.d) corresponding to the runlevels you are interested in using the script.
It might be helpful if you post what you currently have in /etc/rc?.d and /etc/init.d. Do a ls -l so we can see where the symlinks point to.
The actual script should have stop and start sections and these are called as needed. You don't need to write these.
This page about debian runlevels
may be helpful to you.
Sorry this isn't a step by step how to, but I don't know the current state you are in and I am not currently using sys V style scripts (I use BSD style - much simpler in my opinion).