The number of wiki pages is the number of wiki pages on the wiki. Unfortunately moin moin has a behiavior that if you browse to a typoed page it automatically creates a blank wiki page for that which requires us to periodically purge empty pages. It was noted in the announcement.
The ROS community has grown in almost every metric. The one exception is that the number of wiki pages has dropped. This is due to a concerted cleanup effort earlier this year which removed a lot of empty pages with little to no content.
As a meta note, we ask that you please ask questions on http://answers.ros.org following our support guidelines: Support - ROS Wiki
ROS Discourse is for news and general interest discussions. ROS Answers provides a forum which can be filtered by tags to make sure the relevant people can find and/or answer the question, and not overload everyone with hundreds of posts.
In the future please start there.