By default, Geostatistical Analyst interpolates the value of the selected variable at any location that lies within the area defined by the north-south and east-west limits of the sample point data. However, the map of predicted ozone does not cover the geographic extent of California (the ca_outline layer). To overcome this problem, you will extrapolate values (predict values outside the default bounding box) for both surfaces.

Right-click the Trend Removed layer in the table of contents and click Properties. Click the Extent tab. In the Set the extent to text box, choose a custom extent entered below and type the following values for the Visible Extent text boxes:
Top: 860000
Right: -1600000
Left: -2400000
Bottom: -400000
then click OK.

Right-click the Indicator Kriging layer and and click Properties. Click the Extent tab. Set the extent to match the extent of Trend Removed, then click OK.