You’ve probably met someone like this. You’re in a class, for example, and get an A on a very hard class. The smartest person in the class, who happens to be someone you really can’t stand, says, “Well, it wasn’t all that hard a test. I wouldn’t have been able to do so well on it if it had really been hard.” This person is not being egotistical. She really believes that she couldn’t have done well on the test unless it were an easy test. She is genuinely discounting her skills and knowledge.
But she’s also discounting your skill and ability.