DataViz Tip #19: Utilize The Center of Donut Charts
Donut charts are not that different from Pie charts, except for that hole in the center (hence the name). That hole changes the aesthetics of the chart which you may or may not like, but it can also be used for practical purposes. You can display a total value in the center or use it to provide other contextual information.
Here’s an elaborate demo that cleverly uses the center of a donut chart:
In amCharts this is achieved using labels. See the JS code for the demo above to see how to replicate this in your donut chart.