2 different dynos,2 very different numbers.why?

And in some cases, a builder will use inflated numbers as a "sales tool" ....There WAS a well known builder right on this site who I think used that technique, he always made huge power numbers, and all of fabo would oooooooo, and ahhhhhhhh, about his magic, but EVERY one of those builds if ran at the track, would MPH light years off the claimed HP.. Same thing happens with head porters and flow benches. Big numbers SELL