Hey vio,
What this chart means is that the damping characteristics are very linear, which in a nutshell is what you want. The sharper the bump you hit, the more damping the shock provides, which ultimitely helps keep the tire in contact with the road. Also, there is a ratio of 1:3 compression:rebound damping. This ratio is a hotly debated topic, and will vary based on the ratio of sprung/unsprung mass, and the demands you are putting on the bike.
However, understand that you are only looking at the "low speed" to "mid speed" damping characteristics of the shock. Low speed damping means that the rate that the shock is compressing (measure in in/sec) is not very high, which in the real world would correspond to small bumps and undulating road surfaces. Pot hole type bumps which create much more velocity in the suspension and can easily reach rates of up to 25in/sec, and at that rate the damping characteristics may change drastically based upon piston and valving design.
What you see on your chart looks great "on paper," and this is how engineers design suspension, based on what they see on a shock dyno. In real world applications damping rates may need to be altered slightly to work optimally for a specific bike or track. But, this is a great place to start from.
