Does it take into account what filtration you have, if you have any dead spots where detritus or food can sit, how often, how much and what you feed, how large your fish are and how much they eat? I've never heard of that app/program, but I think sometimes common sense and experience trumps a computer. I'm not saying it's wrong, but I would take some of the member's advice here over a program any day.
, you will know when you are overstocked when your filtration can not keep up with bioload and nitrates rise quickly. I also feel there is fish compatibility to take into account.