It was an aptitude test with two sections. One comprising of quantitative questions and other was essay writing.

This is a case study round, in which you are given mathematical data and scenarios from which insightful questions are to be answered strategically.
The most important thing for such rounds is the approach to the problem rather than finding an actual mathematical solution.

Short explanations about the projects you have done, CV debriefing.
Asks questions to check your interest in the profile and your inclination towards it.
Another set of a case would be thrown up to check your approach.

Checks interest in the field.
Asks situational questions to check your response.
Checks problem-solving skills from puzzles.

Ensure good time management for round 1.
Be crystal clear about your CV.