Khalid
Welcome to the forum.
Have you had a look at this
points calculator ?. If you scroll down to page 6 you can see how many points you get for experience as well as for other things.
It is very difficult to understand and try to fit in with the job description codes if you can't find one for your particular job. Is there one that appears to be more or less what you are doing now, even if the job title isn't quite the same as yours? Perhaps you could contact NZIS to ask them how your job title would fit in with those already mentioned on their list.
Good luck.