The WBJEE Board doesnt release the marks and ranks details. SO it tough to predict how many marks are required for getting ranks less than 2000. However, this will also depend upon the difficulty levels of the paper. So I am just giving you an approximate figure of something like 90 to 105. For a very difficult paper the number of marks will be lower like 90 plus and if the difficulty level is easy then you will require to score high marks like 105 above. also the number of students appearing for the exam also matters. 

The rank and score varies in all colleges under WBJEE. You will have to specify the college name and caste category to be precise.