Sorry, but you're wrong. And this isn't simply a question of reading slowly. Read it again, armed with the following fact. What they claim to have been told is

Sorry, but you're wrong. And this isn't simply a question of reading slowly. Read it again, armed with the following fact. What they claim to have been told is correct. It is exponentially hard in N. Your theory is that they meant to say quadratic. This requires: 1. They heard exponential and understood it to be quadratic. 2. While writing down what they heard, they accidentally wrote exponential instead of quadratic. 3. While explaining their question, they failed to catch the second error. Now consider my theory. That they are confused about the difference between exponential and quadratic. This requires: 1. Like many people I've met, that they are confused about the difference between exponential and quadratic. 2. They made no other mistakes. They remembered what they were told correctly. They repeated it correctly. And then asked a reasonable question based on their understanding. In general a whole chain of coincidental errors is far less likely than a single error. Doubly so when it is a single error that is somewhat common. Most people will run across exponential vs quadratic in high school, forget it, then never use that information again. There's an exponent, it's exponential, right? Therefore I think it is far more likely that they misunderstood the term, rather than that they understood the term and then made a whole series of other mistakes to produce the statement that we saw.