Open the dialog box by clicking on the group arrow
in the bottom right corner of the ribbon tab Home | group Paragraph.
The option Suppress line numbers on the Text flow tab has the following function:
By using the ribbon command Layout | Line Numbers (in the group Section), line numbers are displayed in the left margin of the page. If you do not want them to appear for a particular paragraph, simply enable the option Suppress line numbers for that paragraph.
Note: Please note also for your paragraph styles that the option Suppress line numbers must be enabled or disabled there as needed.
For more information on line numbers, see Adding line numbers.