I'd recommend throwing out everything not between 8K-12K. Everything else is irrelevant to the operation of a chainsaw. Also, those spikes, both high and low, are obvious data anomalies. The real number is going to be along a much smoother curve, in line with the rest of the data points. The graph of the HP of an engine results in a curve, generally rising to a single peak at high RPM, then falling of rather quickly.
As mentioned in the discussion elsewhere, I agree that a much more consistent and controllable method of controlling load is going to be needed. That will eliminate all these spikes and valleys.
With that said, I stand in amazement at the knowledge and ability of the guys developing this dyno. No way could I come up with something like this! It's anxious to see where this project ends up. A tool like this would be a tremendous asset to a saw builder. Kudos guys!