You mention in your other post the interview was for a Business Analyst position.
With that in mind, I would reframe the question as:
As a Business Analyst, what does zero mean to you?
A few answers come to mind:
1. "Zero" is very often a special case, needing special handling
For example, suppose you are displaying search results. If you get one result or ten, there is no problem, you display them.
If you get zero results, by default you would see a blank page, and this is bad. Instead, you would at least want a message (which must be written specially) to report "No Results". You might even want search again to look for "similar" matches instead of exact matches.
2. Divide by Zero can often cause problems
Suppose you are running an e-commerce store, and you need to show the price per kg for each product in the store.
If you are selling a digital product, this could legitimately have a weight of zero. It is possible, that the division would cause a poorly built application to crash completely.
As a BA, you should think ahead for this problem, and specify that N/A should be shown, or the field be hidden entirely, if the product has no weight.
3. Zero can often be an indication of bad or missing data
Again, thinking of an e-commerce store. It is possible that an item could have its price set to zero. This is almost certainly a mistake, it is not intended to give the product away for free, and could have been done because the product is still in the process of being created, and a price has not been set yet for the product. There should be filtering in place to hide such products from the customer.
Of course, each of these could be expanded, and you maybe have ideas of your own.
But, all in all, I don't see this as such a bad question.