Hey! Hi Maramasi Arun Kumar.

Let us Understand the concept of UPGRADATION by a following example:

Suppose you filled 5 choices of colleges in the NEET COUNSELLING ROUND - 1.

Suppose you are alloted a college of 4th Preference.

So, in Second round if seats are available then you will be alloted a seat of Higher Preference given by you.

If not possible then your earlier seat will be retained.

And if you are alloted a higher preference seat then this case is called SEAT UPGRADATION.

Hope this helps you.

Thanks.