JoSAA (Joint Seat Allocation Authority) allocates seat in IITs, NITs, IIITs, and GFTIs. The seat in IITs shall be allocated using the JEE (Advanced) rank, while for the rest of colleges will use JEE (Main) rank. You will have to fill the desirable colleges you want to take admission in, while also considering which branch you are interested to study. Once you have filled the list, JoSAA will allocate a seat starting from the first choice you have filled( that is your topmost priority). If suppose you are not getting the no. 1 choice , then it will look for choice no. 2, and so on.. If you are allocated a branch and college at no. 69 in your list, and if you have filled 200 choices, then in the next round JoSAA, will allocate a college in the range 1-68. therefore choices from 70-200 will become null and void. so you should fill it carefully so that the more preferable college(and branch combination) is filled up earlier in the list.

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Hello Rushikesh, JOSAA counseling is done to fill up the remaining seats in IITs, and getting admission in NITs, IIITs and other government-funded technological institutes like Punjab college of engineering and other colleges. You can register for JOSAA from its official website. Its a totally online process, you need to fill in your choices and then you get colleges based on your JEE marks. Last year 10 rounds of counseling took place and more than 50 colleges participated in JOSAA.