So, I was playing around a bit with the watersheds in the Drainage tools in InfraWorks 360 and I decided to do a quick comparison. How do the numbers that InfraWorks comes up with compare with what I get when I calculate them myself. According to the help, the regression analysis uses the USGS National Streamflow Statistics program so, I went and downloaded it. I ran it with the same numbers as I put into InfraWorks and it came up with the exact same answers!
It's always nice to confirm that the magic box is doing what it says it's doing!