You haven't mentioned the exam or counselling regarding which you are enquiring about. But in General, lets say there are 50 seats available for Round 1 out of which 15 seats approximately have been allotted for the Reserved Categories and the rest for General Category. Now if the General Category seats have been filled and there are 5 vacant seats for Reserved Categories. They will be taken forward to Round 2 and then filled accordingly but will not be filled by the Candidates belonging to General Category. This is the norm across all entrance examinations. This is because these are Constitutional reservations and cannot be tampered with. So just to answer your question, if there are vacant seats in Reserved Category after Round 1, they will not be filled by General Category Students. Rather they will be moved forward to Round 2 and filled accordingly by the Candidates belonging to that particular Reserved Category.