About 10 posts. I think people doing the mistake on posts count.
At the start, if you have 40 posts you need at least 50 posts when it is counted. If some of your old messages deleted before, you need to make new of them.
It is not enough just post 10 on that week, your post count should rise at least 10.
Oh, it was like that?
I get it know why people is writing here i did 10 posts and i didn't receive kind of things. The best way is checking the week's participants and see your post count there and act on it.