I replicated this error twice. Once on my local development setup with Magnolia EE 4.4.5 und Forum 1.2.1 aswell as on your demo page http://demo.magnolia-cms.com with Magnolia 4.5.2 and Forum 1.3.1

The thread and reply count is displayed wrong because it also takes objects awaiting moderation into account. The "last message" column is also updated with information from the thread/post that yet has to be validated.