This site will help explain and sometimes decodehttp://www.jewishgen.org/InfoFiles/Manifests/
Once there, click on the box to explain markings in the Occupation Column. Scroll down to see how to find what area the first 2 numbers refer to, depending on the date that is noted on the manifest markings also.
I'm not sure the notations help much when it comes to finding the application for naturalization. At least it didn't help me find a relative in the chicago area.