Not sure if this is a bug, or I'm not understanding something here. llParticleSystem

As the title says, I'm not really sure what's going on here...
What I'd expect this to do would be to create a fan of particles between 90 and 100 degrees, 10 degrees wide...
Instead, what happens is two particle streams are created, at around 90 and 180 degrees, both approximately 10 degrees wide, shooting in opposite directions. I'm pretty stumped as to why this might be. Any ideas?

default
{
    state_entry()
    {
        integer flags = PSYS_PART_EMISSIVE_MASK | PSYS_PART_INTERP_COLOR_MASK | PSYS_PART_INTERP_SCALE_MASK | PSYS_PART_FOLLOW_SRC_MASK | PSYS_PART_FOLLOW_VELOCITY_MASK;
        llParticleSystem([PSYS_PART_FLAGS, flags, 
                          PSYS_PART_START_ALPHA, 1.0,
                          PSYS_PART_END_ALPHA, 1.0,
                          PSYS_PART_START_COLOR, <1.0,1.0,1.0>,
                          PSYS_PART_END_COLOR, <1.0,1.0,1.0>,
                          PSYS_PART_START_SCALE, <0.2,0.2,0.2>, 
                          PSYS_PART_END_SCALE, <0.01,0.01,0.01>, 
                          PSYS_PART_MAX_AGE, 8.0, 
                          PSYS_SRC_ACCEL, <0.0, 0.0, 0.0>,
                          PSYS_SRC_BURST_PART_COUNT, 100,
                          PSYS_SRC_ANGLE_BEGIN, 90 * DEG_TO_RAD,
                          PSYS_SRC_ANGLE_END, 100 * DEG_TO_RAD,
                          PSYS_SRC_BURST_RATE, 0.1,
                          PSYS_SRC_BURST_SPEED_MIN, 0.2,
                          PSYS_SRC_BURST_SPEED_MAX, 0.3,
                          PSYS_SRC_PATTERN, PSYS_SRC_PATTERN_ANGLE]);

    }
    
    on_rez(integer start_param)
    {
        llResetScript();
    }
}

The way the angle pattern works is a little different than you think.

Angle_begin specifies an area in radians where particles are NOT created. angle_end is the overall arc.

You'd want begin to be 0 degrees and end to be 10.