Hey there!

JoSAA counselling is broken down into about 7 rounds. After that, there are still some people who leave the seats for whatever reasoning so they hold a couple of spot rounds where you can get admission if your rank just missed the previous cutoffs. For applying in spot round you have to pay a fee of 35,000 as you've mentioned. So wait till the last round and if you still don't get a seat appear for the spot round. I am attaching the jee main college predictor link so you can see you chances in various colleges

https://engineering.careers360.com/jee-main-college-predictor?icn=QnA&ici=qna_answer