These stand for the names of the different categories

GN=General

GL=Girl

SC=Schedule Caste

SCGL=Schedule Caste Girl Category

The college that you can get through your marks will depend on the category that you belong to. If you are a general category candidate then it will be difficult for you to get a government college. However, if you belong to some category then you can have a chance of gettin into a government college. Although there are also many private colleges that you can go to through upsee. Also you can drop a year to prepare for JEE. Best of luck for your future.