I've changed the way threads and forums are marked as read from the 5 year old out of date system to:
Database (automatic forum marking) which uses the database to store thread and forum read times. This allows accurate read markers to be kept indefinitely.
Forums are automatically marked as read when the last new thread is read.
You will probably find all forums will be mostly marked as unread for the next day or so or until you've visited them for the first time. Once you have finished with a forum you can mark it as read in the
Forum Tools drop down.
I'm sure you'll all figure it out soon enough.
Cheers - Neil