Interview Verbal Case Study

What's your approach when you have an interview and you get a verbal case study?

Let's say they bring up an example of a previous investment in a brick and mortar store or a more simple theoretical example such as a restaurant or food truck. I've ran into a couple of these and I always feel like the interviewer has been wrongly assuming that I know what they're looking for me to think about and address (often the questions following the layout of the example are vague or directionless).

Does that make sense?

Ultimately I get that they're trying to make me explain what items on the P&L are most relevant, what investment strengths/risks I think are at play, and how would you value the company... and I'm very confident in my skill sets and critical thinking in these areas if I get a CIM for example, but I always struggle with these random theoretical examples without detail.

What's your general approach?