Yes, as Conner said "please explain?" The table is just a summary of safety values for the respective sizes and just that. The only problem with it is it doesn't allow for tank depth so it is to be used at your own discretion. It has been pretty close to all the other calculators I have used including the one posted in the same post. I have cross referenced between several calculators including the (
Calculator)Rivermud made and it was in the same ball park figure too. I personally wanted to stay well above a safety rating of 3 so have opted to go with 19mm as posted earlier so I guess it is irrelevant anyway.