Sodium
Sodium is the mineral in salt that labels report either as sodium or as salt, where salt is sodium multiplied by 2.5, and it carries no energy. IZeat does not record sodium; it records calories and the three macros, and the assistant can read a label's sodium or salt line when the customer asks about it.
Sodium is not a macronutrient and has no calories, so it sits outside a calorie record entirely. European labels print salt, American labels sodium in milligrams, and the two are convertible: salt in grams is sodium in grams times 2.5. IZeat keeps neither in the record and says so, rather than showing a zero that would mean unknown.
Sodium is the figure that matters most to some customers and not at all to a calorie total, which is the tension a small honest record resolves by leaving it to the label. Someone who needs to watch it has the label and an assistant that can read it; what IZeat guarantees is that nothing in its record pretends to be a sodium count.
Updated