How to show default values in settings page extended from RecordEditForm

I am building a module and for my module I have a confg settings page (extended from RecordEditForm). I want to know how to add the default value text for each field as in other config pages (like in attached image)

igntion_default

On each field you’ve defined in your PersistentRecord subclass you can call setDefault to set a default value.

Thanks so much. Worked like a charm