From LimeSurvey Manual
Display rows (display_rows)
It sets the number of rows that are displayed without making use of the scroll bar to check all the content. If there are more rows than the number mentioned in this field, then a scroll bar will be displayed. The default value for the "Long free text" question type is 5, while for the "Huge free text question type" is 30.
- Any positive integer number greater than 0