AIShapeConstruction NewEllipticalPie explanation

Can anyone explain the API call of "NewEllipticalPie"?

The call is:

//                    AIAPI AIErr (*NewEllipticalPie)(AIRealPoint center, AIReal width, AIReal height,

//                                                    AIReal rotationAngle, AIReal startAngle, AIReal endAngle,

//                                                    AIBoolean isReversed, AIArtHandle *newArt);

rotationAngle doesn't seem to do anything.

I would expect 90.0 degree start angle to be vertical.

My assumption is that 90.0 start angle and a -90.0 end angle would give a vertical line, but I get the following output with this code:

error = sAIShapeConstruction->NewEllipticalPie(tPoint, circleSize, circleSize, 0.0, 90.0, -90.0, false, &ovalArt);

Output:

error = sAIShapeConstruction->NewEllipticalPie(tPoint, circleSize, circleSize, 180.0, 90.0, -90.0, false, &ovalArt);

Output:

Thanks