Hello Eswar,

The NEET UG 2019 Counseling allows you to choose Medical colleges of your choice. The seat is only confirmed if you fulfil the eligibility criteria. Total number of seats that the college or university offers, the cut off, the category, etc are taken into consideration. You need to know according to the eligibility criteria. The first round is for this. The second round is for confirmation, you could even add your choice again. Mop up round is a round or a list basically that comes out after all the rounds are done. It is for filling all the vacant seats that have been left out after the rounds. 

For more info click on this link given below,

https://medicine.careers360.com/articles/neet-counselling

BEST WISHES!

It seems that your doubt is related to the counselling process and the choice filling. Now when you fill the choises, you have to enter the colleges as per the preference and you will get the institute as per the marks you obtained in the NEET. So it does not mean that you have filled the choices in order then your seat is confirmed. You will only know the seat confirmed when the seat allottment result is declared. So do not keep that impression that your seat is confirmed if you have filled the choices in order.