This come from "Lower Limit on Slice Area" and "Maximum Number of Slices" on the chart properties Presentation tab. I'm guessing you have some values with a very small slice of the pie; try changing the Lower Limit on Slice Area property to 0.001. -Isaiah
In a pie chart the number of slices that you can show is between 2-50. If your slices are more than 50 than it will be put into a "Others" category. Again, the minimum resolution up to which a pie chart can distinctly show the results is 0.01% of the lot. If few of your slices(the number of slices may be less than 50) holds the concerned value less than 0.01%, they will be still grouped into "Others" category.
