Thanks for A2A 🙂
JEE follows a very simple algorithm for seat allocations.
Let’s understand it with an example.
Suppose 10 students sit in the exam. Out of which 8 are declared qualified for counselling. Now the 8 qualified students are asked to fill their seat preferences.
Here in our assumption we’ll try and accommodate all possible cases. Let’s suppose there are 5 seats for which there are 8 students fighting for.
Now after the choice filling is over.
First round of seat allotment:
The choices of the lowest ranked student( Air 1) is seen first in descending order I.e from top to bottom. He/she is allotted a seat. Since he is the top ranked student so obviously he gets the seat which was on top of the choices he filled.
And then the second ranked student is considered likewise. But now, for him one seat is less which was allotted to the student who was ranked 1.
And this process goes on till every seat is occupied. Here we have considered 5 seats, so logically it will go up to rank 5 student. The students at ranks 6,7 and 8 wont be allotted any seat.
Now there may arise a possibility where any of the better ranked candidates fills a choice which is beyond his/her reach( being already occupied by a student having a better rank). This will leave him/her unallotted.
Second round of seat allotment:
Now this round is only meaningful iff any of the allotted candidates pulls out from the seat allocation process, I.e surrenders his/ her seat. And the same process is repeated till each seat is allotted.
The same thing goes on for the reserved seats including rhe home quota till all the seats are allotted.
Hope, it helped. For further information you can refer the website of joint counselling board.
All the best! 🙂