Its easier to understand if you "unfold it" at the zero-crossing, so it looks like a boomerang. Right of zero (velocity) is the compression of the fork, left of zero is rebound. The dyno puts a displacement into the fork to simulate the wheel reacting to hitting a bump, and measures damping force applied by the damping circuits. The velocity will be high for that upward stroke, to quickly absorb the shock and dissipate it before the bike is upset and your teeth fall out. The velocity will be lower for the rebound of the fork, allowing the bike to recover without overshoot, bounce, your stomach stays inside you, etc. The nice smooth slopes show that the forks were very linear and controlled in their responses, meaning the damping circuits work as designed. A cheap shock/fork will have lumpy, non-linear curves and the wrong slopes. There is a bit of hysteresis at the zero crossing, because there is no real damping for tiny movements (that's the tire's job) and there is always some "stiction".
If it rides and handles well, congratulations. If not, it's Thirdway's fault.