Any thread that you have participated in is automatically added to your list of 'subscriptions'. The Top 50 Subscriptions (with 30-Day
activity) is basically just that. The 50 most active threads in your list of subscriptions (Within 30 days of activity).
That list contains threads that have had activity in them within the last thirty days; whether you participated or just subscribed to them. What's
really fun, is if you're subscribed to a thread and it just dies but you don't take it off your list but then, several months later, it appears
again.
excellent question, I'm not only new to this site, but new to blogging as well. I still have all kinds of unanswered questions, but I don't know
enough to figure out what they are....