Hello dear..

maybe in the second round you get your 1st/2nd preferred choice(upgraded only) because just like you left your seat in the 1st round someone left their seat too which was then offered to you since it was your higher preferred choice .this goes on till 4th round of counselling.

then there is a optional spot round too. this doesn’t happen every year. but sometimes yes. suppose ,after all the 4 rounds still few seats are remaining then they are offered to those students who did not get any seat in any round.(this doesn’t mean everyone gets seats it depends on merit)

i hope that is what you wanted to know.

Best of luck...