We don't use servoChangeRate. In our servo library module, we allow specifying a "step rate" for the servo. So you can slow it down. The idea is setting your target servo angle and specifying how long you need to reach that target. For example:
The above code means to turn the wrist up 180 degrees in 1 second2. So it means 180/1 = 180 degree/sec. If your robot loop is running every 100 msec, then it means you should step 18 degrees per loop. It works quite well for us. But obviously, the servo is still moving at its own speed. So the stepping will be moving/stopping on every step. In other words, it looks "robotically jerky". But it does what we want it to do.
According to your code and the RobotC documentation:
You are specifying 10000 which means 10000 positions per update cycle (20 msec). This is very fast, not slowing down. The default is 10. If you want to slow down, you should specify 1. That's the slowest you can get.