How do you format a DesktopChart's y-axis and popup values?

I see the DesktopChart has a formatting ability, but I don’t see how to implement this. There was a Xojo blog post mentioning this, but it doesn’t show how to do it. The dataset values require a double value, so a string cannot be used when setting the dataset

Also, is it possible yet to display the bar values above the bars instead of needing to hover over them?