The default View Intervals are determined by the Domain Intervals and are shown in the Axes & View page of the Plot Properties dialog. To change the View Intervals, remove the checkmark from Default and set the View Intervals by editing the numbers in the boxes. The z-axis can have quite a different scale from the x- and y-axes, and a bounded surface is generally not truncated at the top or bottom. You can check Equal Scaling Along Each Axis to force the same scale on all three axes.