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 tab Layout | Line numbers (in the group Section), you can ensure that line numbers appear 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.
For more information on line numbers, see Adding line numbers.