When a user creates a form, its expiration date will be set by default at this interval in the futur. Ex : if a user creates a form on 01/01/2020 and the expiration value is set to '5', the form will expire by default on 02/05/2020. Insert '0' if you don't want forms to expire.
Here you can change the content of the email that will be sent to the user warning them of expired forms. <i>You can use the following tokens that will be replaced : <strong>[form_url]</strong> (the form URL), <strong>[form_expires_on]</strong> (the form's expiration date), <strong>[form_title]</strong> (the form's title).</i>