Fruits and vegetables vary in size. That's just plain ole common sense. The MC recipe has never been given in amount of lemons but the measured juice of lemons and it is as follows:
2 TBSLP lemon >JUICE<
2 TBLSP maple syrup
1/10th TSP cayenne
8 oz water
BTW 2 TBSP = 1 oz
I'm pretty sure in the book Stanley mentions something about not varying the amount of lemon in the recipe.
In the FAQs at the top of the page there is a recipe for making the recipe in bulk amount which is interpolated from
the above recipe