My original intent was to draw this line as a "line" chart, but it showed up as "dots". See my other post - https://community.tableau.com/message/786441?et=watches.email.thread#786441 . It was suggested that I should use reference line and "per pane". So the line and bar charts can co-exist in the chart. Now I have problem of labeling this line.
Add one more calc field to specify the point of text label display.
Add this field to detail to add one more reference line.
Show reference line only text not line.