Normally, if a newbie start posting, the activity will be counting along until after 14 successful posts, that is exactly what you meant, but after 14 posts, you will notice it is no more counting like what you are thinking, you still have 13 posts, that is the reason you do not know yet. After 14th post, it will only count every 14 days, even if newbie is posting often, when the activity is no more counting, he will have to stop if you think it can result to spamming.
I am not actually understand what you write.
Simply said, activity is capped at 14 for each 14-days period. You post more than 14 posts within 14 days, a max activity point you have is only 14, not more.
The exception is you post 1 post in each 14-days period to
mark that period, then another one for a next period and be inactive for a while. Few months later, you are active again, make 26 posts within a day. When the 1hour-counting is completed, you will get 26 more activity points in 1 hour.
Activity point is counted and updated every hour (perhaps). It seems what you misunderstood.
Can I get more than 14 activity in two week period?
No. However, you can technically get more than 14 activity in a fortnight if you sign up in between periods, but you can't get more than 14 activity in a fortnightly period. For instance, if the period starts on a Wednesday and you sign up on Tuesday you can get 14 points on Tuesday and another 14 on Wednesday providing the period has started. You will then have 28 activity points but won't be able to get any more until two weeks' time when the new period starts.