We’ve seen this before. Turns out that the ordinary kriging algorithm can result in negative weights that may result in interpolated values overshooting or undershooting the maximum or minimum of the original data. This may result in contoured values greater or less than you might have expected. We've added a switch that does not allow the interpolated data to fall outside the limits of your original data. This is activated from the Clip to Data Limit check box in the kriging options of the plan view contour object.