Hi aspirant,

To begin with , a huge congrats for scoring a phenomenal marks in JEE Mains. With this marks, you'll surely get into the best of NITs.

Now coming to your question... JEE Advanced is a different exam altogether and it has often been that students with less marks in Mains scoring extremely well in Advanced. So, it is very difficult to judge how you'll score based on your Mains percentile.

All that said, it is also true, that to score a mark such as 99.89, you need tremendous hard work and a really good knowledge of the subjects, so it can be assumed that you'll definitely score well in Advanced as well.

However, my suggestion would be try solving JEE Advanced mock papers and evaluate yourself, you'll soon reach to a level of perfection.

Checkout sample JEE Advanced papers from the link below.

https://engineering.careers360.com/articles/jee-advanced-question-papers

Hope this was helpful.