I don't understand

What does the nutrion report mean.

Are the percenteges fat carbs etc. the percentege you had out of how much you were supposed to have or are they what percent of your food that day was each thing?

The nutrition report is ... well ... a Nutritional summary of the foods you've put into your Food Log.

By default it does the day's totals, but you can change that if you like.  Just below the "pie" and percentages you will see date drop downs and a button that says, "display report."  Select which dates or date range and CC will show you the Nutritional Report for the given dates.