This explains the math. 140 cal/28g. Prep time http://andrewskurka.com/adventures/alaska-yukon-expedition/f...

Also, on general Considerations in Food Items:

http://andrewskurka.com/2010/the-5000-calories-per-day-wilde...

A worked example in more detail (see "Daily Rations"):

http://andrewskurka.com/2012/food-planning-for-multi-day-hik...