The Drawing Pages in Handset Designer are coordinate-based. Each position (point) on the drawing has an X value and a Y value to mathematically describe its location. The lower left corner of the Drawing Page is the origin point, where X=0 and Y=0. Anything to the right and above the origin is positive; below and to the left is negative, as seen in the picture below:
Although the drawing page is in the positive X and Y axis, this doesn't necessarily mean that you'll always be dealing with positive values. If, for example, you are describing a point that is in reference to another point on the drawing, the origin of the first point may not be at the lower left corner of the drawing. The referring point may be below this first point, which would make the reference a negative value, as in the following example:
For angles, consider the start point to be at the center of a compass and the end point in the direction indicated on the angles there. Anything below the horizontal line is negative.
In addition to viewing the angle from the Size & Position popup, you can also quickly view the angle in the Status bar at the base of the window:
For more information about the Size & Position popup, refer to Using the Size and Position Popup to Edit a Shape.
For more information about drawing guides and setting the rulers to zero, refer to Key Concepts and the Visio help files.