Hello
chandanaca20 , Lakhs of candidates appear every year for JEE Mains from which less than half of the candidates qualify for the JEE Advanced. Around 20000 to 25000 candidates qualify, out of which only 10000 candidates get success to get seat in 23 different IITs. As the number of IITs increasing, seats in IITs also increasing.

Hope it will be helpful for you :)