Depending on the exam all the terms matter. If you go for the upgrade option then it will mean that you are rejecting the allotted seat for a better one. But if there are option such as freeze and upgrade then those options are better. If you select this option then you will be able to preserve your seat as well as you can move on for upgradation.

Now I would recommend you to read the counselling instruction of the examination in order to find the options available in the counselling.

I hope this answer helps. All the very best for your future endeavors!