The Macronutrient breakdown is found next to the Energy Summary on the Diary page.
To change your Macronutrient targets, navigate to the Settings tab then click the Targets Subtab. Learn more in the article Macronutrient Targets.
The percentages listed within the Macronutrient Target bars indicate the percentage of your goal for each macronutrient. By default these bars will show your macronutrient breakdown for all items logged in your diary.
To see the macronutrient breakdown of a specific food or multiple foods, make a selection in your diary. The Macronutrient target bars will fill up based on the item(s) you have selected. To revert back to complete day breakdown, click on your selection again or click elsewhere in the diary screen.
If the default Fixed Targets are used, the four macro bars will all show fixed gram amounts which you can configure by clicking on the bars.
For all other Dynamic Macronutrient Target selections, the targets will be dynamically calculated throughout the day based on several factors. The energy target will be derived dynamically by looking at your total energy burned for the day (BMR, activity, exercise, etc.) as well as your weight goal.
For example, if your daily burn is 2200 kcal, and your weight loss goal is to lose 0.6 lbs per week, this requires a 299 kcal energy deficit, and so your energy target for the day will be set to 1901 kcal (2200 - 299). The protein, carbohydrate, and fat targets will then be derived based on the chosen ratio to balance at your energy target.