Madoka does think that with the way Wangji says it, it's like he's implying that anyone could do it. Even Madoka herself. Which is an amazing idea, but at the same time she isn't so sure if that's true.. Maybe it's only true about people from his world. Madoka can't imagine herself being able to do something this amazing..

But she doesn't pipe up with that, not wanting to drag down the mood by bringing any of that up.

Instead she just says: "You must have had a lot of time to practice it.."

You know, since Wangji is apparently just that old. Her mind is still kind of marveling over that fact.