total posts are not activity,
but activity is part of the total posts.
activity will be updated every 2 weeks and maximum increasing in activity are 15.
so no matter what how much posts that you made in the past few days it will not change the fact that it will only increase in the next 2 weeks.
it's not a problem but it's the rule.
read here about this :
RANK and Othersplus your posts were not 39 but it's 38,
and it need a hour to change the activity in your account