Okay I can respect that I'm not trying to argue with you but that's what the number show... issues with algae, detritus, fish waste, completely depends on husbandry the type of fish you have, how much you're feeding, cleanup crew, a bunch of other factors, I wouldn't necessarily contribute those factors to the amount of flow in the tank however flow is required to maintain a healthy tank.
Those numbers are based on turnover, whats in the tank, not turn over through the sump back to the tank those are completely different calculation and based on the fact that you're going to be running a mixed reef with soft corals and LPS, 390 rounded up to 400 should be enough but that's just my opinion.