Think that you've just made a Skype call. You superior has just referred to some figures for a reception: how many guests will come and how many rooms should be reserved. You are confident that you can keep those figures in mind and didn't jog them down. Then you make a call to the hotel, and your mind gets stuck when the other side asks for the number of visitors. Ask your boss for the number again? You will not seem so adequate for your work.