Fixes #7747. some doc

extension/Source/core/Save.php

@@ -669,6 +669,7 @@ class Save {
             $importNamedSheetsOnly = explode(',', $formElement[FE_IMPORT_NAMED_SHEETS_ONLY]);
         }
 
+        // Check for keywords which needs an explicit given document type.
         if ($formElement[FE_IMPORT_TYPE] === FE_IMPORT_TYPE_AUTO) {
 
             $list = [FE_IMPORT_LIST_SHEET_NAMES, FE_IMPORT_READ_DATA_ONLY, FE_IMPORT_LIST_SHEET_NAMES];