Well, I'm not feeling like reading all of that right now and the math is beyond my current skills.
From the bit I read however I think they are determining the largest size an organism could be based on the laws of physics.
Just like a deep sea creature explodes when you pull them to the surface, or how you would be crushed to death on a high gravity planet I think they are trying to say that based on the components of the universe, ie, atoms, there is a limit to how big a living being can be and still function. Steel, wood, and cement, all used in construction have limits to how much they can hold and my guess is they are saying there is a limit to how much a carbon based life form can take and still run? Thus, I guess a limit to how tall a Giraffe can be?
That's my gut reaction after reading a paragraph and is likely totally wrong. Maybe one of our resident Physicists will come along and open our eyes.
What I really wonder is how much money they got for doing this study and how you came upon it