Have been wanting to ask why is it that most users here their activity is different from their post count. For example you will see some user having the post count of 500 with activity of 125 why is it like that and what Is the course?
You can make many posts you want if you have time with small limitations on minimum waiting time between two posts. With higher forum ranks, you will have less limitation of waiting time (shorter waiting time).
However, limitations on maximum activity point for an account is the same for all ranks. Each account can have a maximum of 14 activity points within 14 days period. You can make 100 posts within 14 days period but you will gain only 14 activity points.
Difference you ask is from these limitations.
You can use the spreadsheet to see activity point updating time.
https://docs.google.com/spreadsheets/d/12saLhlUoqIdairxzuSPu6EYGrt7FN2lOstO1yDjCEbA/edit?pli=1#gid=1012758442