When we are reading the prospectus of any college either it’s an engineering or any other Science or Art college. They usually write about the number of seats in each branch or stream for any particular degree or diploma. If we only talk about engineering college so during the starting of a session they fill almost all the seats through the entrance examination. But after few weeks they usually increase the seats in few of the branches (Only private college, not the reputed one) based on the interest of students and they usually give horizontal transfer to the interested students from their old branch. Because of that, there are vacant seats in that old branch which can be filled by new students and that can be advertised as vacant seats. Because they are doing this, they keep a track that how many students they had enrolled in each branch. Sometimes they do it intentionally because they know in few branches placements are good and they can attract more students so they increase the seats in that branch.

In another way; when students write their entrance exam, they write it for different Universities and wait for the result and meanwhile they register them selves in any University. With time they get the results for the rest of entrance examination and based on that they select another college or University and they left the seat. So that seat also comes in the list of vacant seats. Govt and other renowned institutes provide those seats to the waiting list candidate. So if there is any vacant seat, students in waiting list will get preference according to their rank in the waiting list. It is necessary for an Institute to fill that vacant seat otherwise that seat will remain vacant for next four years.