In the Guidelines and Standards for Tactile Graphics, there is an extensive section (6.5)on number lines. Specifically, 18.104.22.168 says that a number above the number line must use the numeric indicator (regardless of whether the text is transcribed in literary or Nemeth. Page 6-23 of this section also shows an example. Your example [u]looks[/u] as though you have a blank line above and below the axis line. There should be a blank line above the first row of numbers, followed by the axis line, then the numbers below the axis line, and then followed by a blank line.
Hope this helps!