Cracking the examination do not guarantee seat in a top institution. Furthermore to land in a branch like Computer Science, the race is even tough. A rank around 30,000 guarantee a very good institution such as NIT or IIIT where as a rank within 1,00,000 can land you in a decent branch in a good government institution. The requirement varies depending on the home state advantage. While the above is true for JEE Main, a rank within 10,000 is required to land into an IIT, IISc and other reputed institutes. The top 7 IITs demand an even lower rank around 4,000 depending on the branch of choice.
IIT has a total number of 11279 seats, 31 NITs have 17967 seats, 25 IIITs have 4023 seats and other 23 GFTIs have 4683 seats. Popular Private institutes also admit students based on the JEE Main rank and can be checked individually.