PlumCity says that they translated up to chapter 7 on their website and their IRC channel. Why does it say Chapter 15 has been released on this website?

Can I ask how you know they're on chapter number 15?

When you come to a fork in the road, take it. - Yogi Berra

The 15th chapter if you start counting from volume 1
The 7th chapter if you count ch1 as the first chapter of volume 2

A just ruler amongst tyrants

someone else, another scanlator, has probably already done it up to chapter 15
there should be a list of scanlators working on the manga in the series info
you can probably find who's done which chapters there

Counting from the first volume...now I feel stupid, lol.

Thanks for the clarification.

When you come to a fork in the road, take it. - Yogi Berra