Trying to create simple bar chart with Chart.js

On one of the pages I’m creating using Bubble, I have a % field that is calculated.

Below that % field, I want to display a flat bar chart that displays the %. Upward green bar if the % is positive. Downward red bar if the % is negative.

Here’s a visual example:
http://www.screencast.com/t/XxXhOluc

I’m not clear on what to select for Data source and value expression:

And can I leave the Label expression field blank, if I don’t want any labels to appear?

Thanks to anyone who can help!!!

George