What to include
One fact per report: which page and which value is wrong, the correct value, and a public link that shows it, such as a Modrinth version page, a changelog or the source repository.
What happens next
The source is compared with the current Modrinth listing. Facts come from Modrinth, so a value that is wrong there is fixed on Modrinth by the project owner; the catalog picks it up on the next parse and the "Facts verified" date changes.