littleBits servos work differently from other servos, because there is an attiny chip on board that helps control its movement.
Try setting the micro-switch on the servo to “turn” mode and control it with a dimmer module before it.
"In turn mode, you can control which direction the servo arms point. The servo listens to how much voltage you give it, and moves to the specific position. As you increase the voltage (electrical intensity), the arm turns clockwise; decreasing voltage turns the arm counter-clockwise.
If you use the simple circuit: power + dimmer + servo (turn mode), the servo arm will follow the turns of the dimmer knob." Tips & Tricks: Servo
(pic by @alexpikkert)
Now, still in turn mode, try using the servo with your CodeBit and %. How does that work for you?
P.S. If someone knows of a CodeBit sample project that uses the servo Bit, could you please reply with a link?