Hey aspirant,

The casual vacancy round is also known as Mop - Up round or the Spot Rounds are conducted after all the normal rounds only if there are vacant seats remaining after the normal counselling rounds.

Whereas in second extended round , same as previous rounds , some people render their seats for their personal reasons which will create a vacancy which is filled in second extended round.

Here , i mention the link kindly go through this link:

https://engineering.careers360.com/articles/kcet-seat-allotment

I hope it helps you. Revert here if any query.

Thank you :-)