Data format for 'Progress' visualisation?

Hi
I am trying to get a progress bar visualisation for a KPI. I am writing SQL to get two numbers, an actual and a target but the ‘progress’ option is greyed out and when i click it i get a green bar taking the first number as both the goal and target.

What is the ideal data input format for it?
Was unable to find this in the documentation.

I found the answer.
The progress visualisation needs only a number input and then the static goal has to be set from the settings icon after choosing this visualisation. This was not obvious to me.
The latest documentation http://www.metabase.com/docs/v0.20.3/users-guide/04-visualizing-results.html doesn’t mention this at all and infact doesn’t even mention ‘progress’ as an visualization option. I would be up for updating the documentation if anyone can guide me how to?