A dyno is a tool best used for A-B comparisons for the engine and the changes made. Not a dyno vs dyno.
As long as the operator is good with the calibration when he tests, it is what it is. And comparable to another dyno it is not. It should (key word there) be in the same ball park. A 40 hp or lbs difference is a lot. Assume it is the same dyno that this engine is being tested on. A different engine can easily dyno this difference with the machining talents & exact parts used.
I don’t put a lot of faith in what anybody’s dyno reads. To many variables.