Concerning plugin version 4.0.3
Be aware that more then 1000 Codes will produce a php warning:
PHP Warning: Unknown: Input variables exceeded 1000
This ends up in losing the ability to save your options for this plugin via the backend.
You can only save your options by modifying the tbl _options directly.
You could increase max_input_vars in your php.ini but I don’t recommend this for productive systems.