Where are you getting those numbers?

In my experience, bhp is pretty useless as a measure of how an engine actually pulls your plane. Way back in the day, engine makers and reviews would hook up engines to dynometers to get real HP numbers. But they discovered along the way that it wasn't really all that helpful when picking an engine anyway, so no one bothers with that anymore.

Also, most thrust calculators I've seen are "best guess" or have built in assumptions that might or might match your personal reality. For example, all engines "unload" a bit in the air, and pick up some RPM once off the ground. However, not all engines unload the same, not all props unload the same, and the weather conditions and air density at the moment can really affect things as well.

I'm not saying the numbers are wrong, I just want to know the source.