My brother appeared for the interview last year, so I think I can answer your question.
The panelists will evaluate your ability to explain new questions. They might even ask you to solve the questions on the board. You must be clear about your choice of ISI Kolkata as you will be asked the reason for the same during the interview.
Expect questions on topics such as Calculus, Geometry, Combinatorics, and Probability. Keep your basics clear, know the definitions, and practice solving problems based on the definitions.
Just keep practicing, be confident and give your best shot at the interview.
Kolkata is one of India's safest cities. This city attracts visitors from all over India and the world. That's why it's known as the "City of Joy." Bengalis are extremely friendly.
ISI Kolkata is known to have the most sought-after institute in Statistical expertise. It has one of the best faculty members in India. Out of which, 30 professors were published in Standford University.
Moreover, you have got a seat in B.Stat which is considered one of the toughest examinations for Mathematics in Asia. You should base your judgement on the basis of a stereotype as letting go of this opportunity will be a wrong decision.
Almost 50% of the batch consists of Non-Bengalis here at ISI Kolkata. There is no need to worry as the institute also has a rigid anti-ragging policy.