Contact
The most useful message names the page and the figure. The pipeline is automated, so a wrong number is usually wrong on many pages at once, and one good report fixes all of them on the next rebuild.
Email [email protected], or use the form; they land in the same place.
What is kept: your message, the name and reply address if you gave them, and a salted hash used only to slow down bulk abuse. No account, no tracking, and nothing you send is ever published.