This is a sweet little story, exactly described by its title. The professor in question is an elderly mathematician who has had a brain injury that has left him with only 80 minutes of short-term memory. The housekeeper, therefor, has to introduce herself to him every morning when she arrives at his house.
She has a son who comes along sometimes, and there are maths puzzles and baseball.
It doesn’t sound like much from that description, and it’s very short. But it’s thoroughly compelling and enjoyable.