Refs https://github.com/getgrav/grav-plugin-data-manager/issues/5

What happened is that pages added by plugins in the admin get counted
as normal site pages. Counting only routable and modular pages solves
the issue without messing with iterating over page types added by
plugins

classes/admin.php

@@ -384,6 +384,19 @@ class Admin
         }
         return $routes;
     }
+    
+    /**
+     * Count the pages
+     *
+     * @return array
+     */
+    public function countPages()
+    {
+        $routable = $this->grav['pages']->all()->routable();
+        $modular = $this->grav['pages']->all()->modular();
+
+        return count($routable) + count($modular);
+    }
 
     /**
      * Get All template types