Based on what I have see it is making a really good approximation. Here is a thought problem: if memorized every single result of of a multiplication between two numbers up to the maximum a human can possibly think of, then do I understand multiplication?
My point about mistakes is not that they were made but the way they were made indicates it was attempting to approximate. Someone mentioned a famous mathematician who got basic multiplication wrong, now if you are wrong because you missed some steps in the process that can be proven. But if your mistake is because you guessed the that can also proven by showing defects in your answer were arbitrary.
Pretend you're grading a student, you can tell when they guessed and got it wrong as opposed to tried to follow the process bur misunderstood something or make a critical error.