We look at the overall balance of your receipt. So if you reach 100% on each of the five food groups (see also Q2), you get 100 points. The purpose is therefore to reach the 100% with one or more receipts in a week. This also to say that, we do not assign points per item, for example bananas are not equivalent to 10 points. The reason is that with this model (which, we realize, is commonly used for its simplicity), eating lots of bananas would give you lots of points but not a balanced nutrition, and therefore your body would still be missing most of the nutrients it needs. A healthy diet is a balanced diet, which is what we are trying to reward.
The USDA has released its 2016 recommendations on what a balance diet should be, namely how many cups of fruits, vegetables, grains, proteins, etc. These recommendations depend on the person’s age, gender, exercise level, and a few more parameters. For simplicity, we are only using the first three for now. So based on your household, we compute the USDA recommended quantities and we present them to you as weekly objectives (the reason is that people usually do not shop for a single day). So the 100% bar means “the amount that you should have in a week”.
From your receipt for example. it appears that you purchased enough proteins for the week already (in fact, a bit too much), pretty much your exact needs in vegetables, but you will need to purchase more fruits, grains, and dairy to balance your nutrition this week.
In a similar way as food groups, the USDA has recommendations for quantities of macro and micro-nutrients, which we summarize in the nutrition fact label. Here as well these are quantities for a week so for example, it appears that you purchase about half of the calories you would need this week.