breaking down a slice of a pie chart

I don't know of a way to do this just using Chart features. The quickest solution is to use shadow data to make the chart, if you want your data table to stay the way it is. Please see added sheet "Chart Data", and I have modified the chart to use that data instead. You would use the same strategy for the second chart.

This is more of a brainstorm than a final solution but I think it's a step closer. I have created a second pie chart that is superimposed over the first. But I haven't figured out how to show the number for data value that you want, which is the percent of Asia represented by China.

The approach is to define a new chart that calculates the percent of the entire world represented by China, then create a single slice for that. Two more slices are needed to fill out to 100% so I create a first slice of the appropriate size to place the China slice where I want it, then make the third slice to fill it out to 100%. These two slices are formatted with no fill so as to be invisible. Their data labels are also blank so they don't show up in the legend.

Frankly I think it would be easier to include China in the first place, with calculations to subtract it from the Asia part to make the numbers work out.

I was not able to figure out how to do this in a single chart, though Andy Pope the Chart King may know how.

Here is an improved version that provides an automatic caption for the China data point. The caption is dynamic, so any change in the percentage will be taken care of.