Here's the deal, it may be a very nice inertia dyno, but it's instrumentation package is very old, which is why I called it a POS. Inertia dynos in general are not very accurate and are used more for tuning than benchmarking power. An inertia dyno basically measures how long it takes for a flywheel to reach a certain speed and then extrapolates hp and torque from that time given the known weight of the flywheel.
With that said, water or oil brake impeller type dynos are where its at due to thei ability to read much more accurately, react to atmospheric deviance, and vary the load on the dyno specimen. In addition, they usually come better instrumented.
There is a third kind of dyno out there that you will see, known as a mechanical brake dyno, this is like a water or oil brake dyno except is usec a large disc brake pack to load the specimen. You can see where this type of dyno goes wrong, but oncae again you could certainly tune on this type of dyno.
If you live anywhere near WA, you can come roll on my work's dyno whenever you want.