^^^
Read the link posted above. Any website info you need can be found in the "Meta" forum.
The activity number is determined in this way:
time = number of two-week periods in which you've posted since your registration
activity = min(time * 14, posts)
Activity is updated every hour.
No. The potential activity increment is every 2 weeks in unix time, the schedule can be found here:
https://docs.google.com/spreadsheets/d/12saLhlUoqIdairxzuSPu6EYGrt7FN2lOstO1yDjCEbA/edit?pref=2&pli=1#gid=1012758442.
You need to post at least once in a two week period to get the 14 potential activity. The activity will be equal to your total post count. So eg. if you have posted at least once in two 2 weeks period, you will gain 28 potential activity but if your post is 3, the activity will only be three. You can post more till you have 28 post and the activity will correspond to the activity that you have gained.
