I'm an old user! and willing to help you set up a burndown chart from leankit. Your question is?
To create a typical burn down chart showing cards completed over a time horizon from leankit data how do you setup the data sources, columns, rows, etc...
What data within LeanKit are you accessing? If you're an Advanced or Premium customer you should have the ability to have an Advanced Reporting Site set up with access to native Tableau data sources that would make this much easier. We are also working on a beta version of a Reporting API that will allow for simpler programmatic access to these types of data - this capability is set to be released early next year (Q1 2017).
LeanKit also provides an in-app Burndown visualization for Select, Advanced, and Premium edition customers that should be accessible via the Analytics icon in the top-right corner of any LeanKit board. Please check out the following link for more information: Burndown chart – LeanKit Help & Support
I'd be happy to give you advice and/or help you on your journey to discover useful charts and create actionable information out of your LeanKit account! Please let me know what specific questions you (or others) have and we'll work through them together!
For transparency sake, I should probably tell you that my name is Chris Gundersen and I'm the Director of Analytics at LeanKit.