it just adds it to it on that frame and then the next time it does the addition (on the next frame) the value has already been updated so it just adds another 30 on... it's just a counter really nothing hard.

If you wanted it to be a bit more "animatable":

add an attribute called "speed" and then set the rotateX to be

rotateX += speed;

That way you can key the speed attr which will control the speed of the prop.

:ninja;
Alan