Incorrect count using trackGoal

Firstly, what a great piece of software! Congratulations.

Like many others, I am totally frustrated by Google Analytics not recording my ecommerce sales data promptly IF AT ALL!

It was refreshing to see accurate data within minutes of installing Piwik.

However, yesterday Piwik counted one of my sales transactions twice. Obviously, no-one can comment on that, but if I could have some guidance on how to debug the database, I may be able to provide more information.

Also, is there a way of getting my sales Goal Widget to chart sales value and not the count of sales? ( EDIT Solved: Just click on the legend ! )