You need to break up some text entered in as a field default value expression across multiple lines i.e. usage of \r \n. However the email notification that gets sent with this text in the email body appears as a single line of text rather than across multiple lines / paragraphs.
"Text, Number or Mask Field" controls do not support carriage returns or line feeds in stored data. Any such characters entered into the field value using \r\n expression syntax will be stripped from the saved data.