Classifing ESRI's World Elevation Layer does provide full spectrum of values

[SamsonLee]

Anyone happen to know why I might not be able to might classify the ESRI world elevation imagery layer's slop in percent from the ranges of 0-1000?  

I go to the layer in the webmap viewer to adjust the imagery display options.  When I set the Renderer at Slope_Percent, Image Enhancement Symbology Type of Stretch, I can see the entire world covered with visual data.  As soon as I apply a Image Enhancement Symbology Type of Classify with the Field: Value, Method: Natural Breaks, Classes: 5, the upper value caps out at <= 25.5.  I would expect this value to be <=1000.  Any reason for this occurence?

Note: No filters of the layer have been applied so I do expect that all records should be visible.