Fix total number error. (#4339)

### What problem does this PR solve?

#4328

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

api/db/services/document_service.py

@@ -66,8 +66,8 @@ class DocumentService(CommonService):
         else:
             docs = docs.order_by(cls.model.getter_by(orderby).asc())
 
-        docs = docs.paginate(page_number, items_per_page)
         count = docs.count()
+        docs = docs.paginate(page_number, items_per_page)
         return list(docs.dicts()), count
 
     @classmethod