Questions about software and portals

DNAnutriPlus portal

Why does the portal mention servings and weight, and not items, the way the booklet does? I find this quite confusing.

There are 0 food items which are considered in the booklet as an arbitrary number, but when I incorporate this in a menu or change other foods, this article is also changed and suddenly goes from +++ g to 432 g. I don't understand this.