Did any of you horsepower calculator guys ever use this

What I noticed on my 340 is it sure liked duration with my setup. I punched in a couple of my different camshafts and was able to jump up nearly 50 horses with what I thought was relatively small increases maybe two stages. I have never done any desktop dyno stuff so it was fun for me. Too many variables to consider it extremely accurate but I will say I believe it's ballpark.