The 4% is the "of Pie" portion of the "Pie of Pie" chart you're using. As the description states, it breaks out the smallest slice into a subpie so it is easier to see values that otherwise would have been too small to see in the larger pie.
If you don't want the subpie then select the chart and change the type to Pie. This shows you a traditional, single pie with all the slices.