User blog comment:IamJakuhoRaikoben/Chapter 487: The Third Seal, Review./@comment-4507125-20160603184009/@comment-7418318-20160605155539

I think it was just an overly dramatic way to say that both August and Irene are in a league of their own, far ahead of anyone else, even though August has her beat in strength to at least some degree.

Why would you think her levels fluctuate based on what Brandish said?

Though if she really uses the magic from the land surrounding her, like Zeref's comment indicates, that might very well be true, depending on her location.