Hi, the page Special:Statistics lists the number of content pages.
The number is updated twice a month: initSiteStats.php is run at 05:39 UTC on 1st and 15th of each month.
According to configuration, wgArticleCountMethod is set to link for this wiki. That means that a page must contain a wikilink to be included in the content page count. So the number might be lower than you expected.
I don't think there is a bug here.
I will show the information. I had recorded of the number was 162 articles as of Sep. 1st, now, the number is 46.
The existing page has not many moved and deleted significantly, so I think the value is clearly abnormal.