hi sanjay,

in first round -> some of the candidates above your rank who had taken an admission in COMEDK first round but later got some other college somewhere else, so they opt out and withdraw from COMEDK leaving a vacant space which will be taken by later rank holders. So, in the Second round of Counselling, you may get some better colleges, or may be some better branch of your choice.

Usually a difference of 1000 ranks is seen in between both the rounds.

Eg:- Like for someone having 5000 rank will get mechanical in 1st round but holds a very high chance of getting upgraded to ECE in 2nd counselling.

hope it helped!

all the best!