Dear Honey Soni,

JEE Advanced maximum marks are not defined :

Maximum Marks vary every year like below:

2017- 366 

2016- 372

2015 - 504

2014 - 360

So, it is difficult to predict marks as exam pattern and marks change every year but you should score more than 50% marks to get good branch in Top IITs.

According, to 2017 cut off you rank should be under 62 to get CSE branch in IIT Bombay in general category. 

Good Luck!!

https://engineering.careers360.com/articles/jee-advanced-cutoff-for-iit-bombay

our link will help for your question

All the Best for your future