dyno hp ratings

We had a tractor dyno'd on a friend's dyno the other day. He had a line on a rpm dial that I assumed was 540 rpm. When the engine was put under load and the rpm's dropped to the 540 line on dial, that was the level where we read the hp rating on another guage (which happened to be 45 hp for our tractor). When he really loaded the engine and the engine rpm's lugged down to 1300 to 1400 (est.), the guage for the hp read in the 55 to 60 range.

My question is which hp rating should we go by? I am assuming the we whould use the 45 hp rating instead of the 60hp, but is this an example of where some people can come up with some almost unbelievable hp claims for their tractors? Thanks for your responses.