JOSAA Counselling Process

Here is a link that describes the process:
https://engineering.careers360.com/articles/josaa-counselling

• There will be 2 rounds of mock seat allotment before the due date of filing choices. 
• There will be 7 rounds of seat allotment and after each round allocation is adjusted to reflect number of candidates not opting for the seats which they got. So your preferences go up in the allotment system.

Here is a good Quora answer that tells some tips for the process:

https://www.quora.com/What-are-some-tips-to-fill-choices-in-JoSAA-counselling

You can try to predict the college allotment according to this tool:
Rank to college predictor:
https://engineering.careers360.com/jee-main-college-predictor