If you ever changed your password then the updated version might only have been saved for the forum. You can go to wherever your password is being stored to retrieve the username and password for forums.j-novel.club, e.g. https://passwords.google.com/ for Google Chrome and the saved passwords section of Firefox.
The book publisher has almost no control over filing such as this. This is something you’ll need to complain to Amazon about (good luck). At least it’s not hidden behind the pre-existing manga version like The Ideal Sponger Life.
@rahul-balaggan on the one hand I was thinking someone probably needs to audit the descriptions against the actual list since there seem to be a lot of them that had the wrong date when the new site went live. On the other hand, all of the ones that are wrong had April 15 on them, which means the problem is probably fixing itself in 2 days anyway.
I just looked at my library and that is the only series with this unique numbering "feature". Could be the new website or how that series is entered into the database. may need to be posted in the new website bugs