Okay. I'm going to try to translate this as I understand it; somebody tell me if I get it wrong.

The body powers itself by burning available fuel (carbohydrates, stored in the blood as glucose[?]) and by converting stored fat into available fuel and then burning that. Any available fuel that is not burned is stored as fat.

The fuel usage continues at a given ratio (available fuel/stored fuel). This ratio varies, depending on the person. As the heart rate increases (presumably in response to increased activity), the fuel burn increases, the demand on available fuel increases, and so the ratio changes. Wild guess: the body can't convert fat quickly enough to meet the demand, hence the need for increased carbohydrate intake to avoid depleting blood sugar? This would explain why the number of fat calories burned does not increase dramatically -- it can't, because the conversion process can't speed up dramatically.

I do wonder about the third line on that chart, though. The math doesn't work -- is that a typo?

40% fat + 5% protein + 50%-85% carb = 95%-130%; that's okay, because the possible sums include the 100% that the numbers are supposed to add up to. However,

60% fat + 5% protein + 50%-85% carb = 115%-150%; 100% is not a possible solution to that equation, no matter how you slice it. Something is wrong somewhere.