THIS (and stay with me): The app suggests you food for each meal. For breakfast it suggests (example) an omelette with mushrooms 1 slice of bread and a fruit of your choice. You can then eat what it suggested or not include some things for exhample mushrooms or fruit. You can eat something different even it doesn't matter (but the suggestions are important). What the user does is he enters what he ate for that meal. lets say you ate what the app suggested so you enter that. If you didn't eat the slice of bread or fruit you leave that out - accuracy is important.

So what the app does it takes what you ate and makes the next suggestion based off of that (and perhaps even when you should eat next). So since you didn't eat any fruit for breakfast at 6 AM it suggests fruit for a snack at 10AM, if you ate all of the things it suggested it continues normally for lunch at 2PM some pasta with vegetables. REMEMBER you are putting what you ate inside the app so it knows and tracks it.

Now the first path was according to plan but lets say you craved some sweetness in the morning so you decide to smear nutella on 3 pieces of bread. The app adjusts the suggestions to let you know you already ate a lot of calories and will have to eat lightly if you want to finish your day with a normal caloric intake and eat the nutrients you require. So it changes the suggestions accordingly fruit snack at 10AM a vegetable soup for lunch and maybe a fish for dinner.

Sorry for unorganized text/mistakes I had to write this up fast. Hopefully it makes sense.