What are 9 degrees of freedom in robotics?

I think that the other three with that module are the outputs from the magnetometer.

As I read the description I guess they just added the signals that are measured: 3 gyros (orientation) + 3 accelerometers + 3 magnetic field sensors = 9. Makes no sense to me, the gyros and magnetic field sensors essentially measure the same thing (orientation), although I think gyro's are more usefull for small changes, and magnetic field sensors are better for long term stability, so they complement each other.

But adding it all up to 9 is sales speak in my book. They might as well add a temperature sensor and call it a 10 DOF board.