Potential activity is the number of activity you can have in a period of time. In 14 days an account can have a maximum 14 activity increase if he posted 14 posts. Now if an acxount only posted 1 post in that time of activity increase, the rest 13 activity will not be added to the account not until you could cover up the 13 post. So if you can post only once in every activity update, you will gain a lot of potential activity and you can get all that activity if you posted the same numbers as the pot activity you have. You do not have to wait for the 2 weeks period.