The page count only counts pages in certain namespaces. In addition, it is subject to caching. As such, the number that is displayed is not always the exact count at that very moment. Caching is used to reduce the computation power needed from the server as well as increase the speed with which the page will load for viewers. The downside is that what you see is not always the most recent information.
Ah, you mean Discussions (a.k.a. Community Feed)? Yes, they are replacing Forums and your wiki already has them. If what you meant to ask is how you create the different Disucssion categories, read this.