Can anybody explain what is potential activity? The difference between the number of posts and activity?
Not really. You only need to make one post to be able to collect the full 14 activity at a later date. So if you made one post each in two seperate periods you would have 2 posts and 2 activity but a potential activity of 28. Once you made a total of 28 posts you would then get the full 28 activity but no more until the next period.