People who don't know any better often use the words editing and proofreading interchangeably, but they don't mean the same thing. I tend to ignore this error — I usually know what they're talking about, but maybe you don't. Maybe you're one of those people who just bandies the two words about interchangeably. If so, it's OK. I won't judge you too harshly. And in some environments, editors are expected to do both at the same time. But just so you know what you're talking about going forward, take a look at this infographic from Scribendi.