Hello

You will be called for counselling on the basis of your All India Merit Rank. After your counselling and checking/ verification of documents you will be assigned a seat based on your AIR or your categorty rank (which ever will help you get the seat).

Suppose you get a rank of 100 and you want to take admission in Calcutta Medical College. Now for UR (AIR) there are only 30 seats (Let us assume) then you will not get that seat but there are 27 seats reserved for OBCSupoose in the number of students who have gone for counselling here there are only 20 OBC students who have higher marks than you so you will get a seat under OBC reservation (If you prove that you belong to that category).

I hope it is clear now. All the best!