It isn't "altitude", it is ATTITUDE. Dang, John beat me by a minute.
And it doesn't even hold the attitude, it just holds the cyclic in one spot - the attitude can change but the cyclic will not correct itself - unless it is fitted with an autopilot.
The cyclic plot shows that at low speeds, there is a bit of left cyclic needed to overcome inflow roll, and more forward stick is needed to maintain speed against flapback.