Sorry I was doing my calculation in cubic feet originally, I should have replaced the 27 with 1 when I converted to cubic yards. The rest of the values are numbers are correct). We are talking about 1 cubic yard per SHIFT of 8 hours or 3-4 cubic feet per hour (including rest stops etc.)
If you are not willing to quote rules you could quote page references as we don't know what special circumstances you have applied if you don't share them. Which chart for example. You could have set out your maths in your response just like I did. Then it can be examined and verified if necessary (and typo's identified). You are not breaking copyright by putting some maths down.
I did buy Pirates of Drinax and I have the read them (not necessarily committed all of it to memory of course so I am as liable to error as anyone else).