"Last visit" indicator in a forum

In each forum there’s a thin red line followed by “last visit”. This useful feature seems like a really simple thing to ascertain by Discourse. But apparently it’s not, as it can be wrong by several hours. Recently I was away for about 24 hours, yet in each forum my “last visit” went back only 6 hours. Why can’t this inaccuracy be corrected?

Did you have multiple devices open browsing the website? Or multiple tabs in the same browser? That’s usually the reason.

“Presence” is a 10 minute window where no web browser (where you are logged in as you) has pinged the website.

No, I use only one device, an iMac, and only one tab open. I’m still finding threads beneath the red line that I’ve never seen.

I was just away for about 24 hours. All the “last visit” lines are at 2 hours ago.