Serving Size is on the Prices table, one box per portion size, and answers "how many people does this portion serve?" (shown as a tooltip on the column header). It is plain text, not a price or quantity field, and is shown to customers and printed on labels alongside that portion. It only accepts numbers, spaces and hyphens - so a single number ("4") or a range ("10 - 20") both work, but letters or other punctuation are rejected with "The Serving Size field may only contain numbers, spaces, and hyphens". Each portion size keeps its own serving size, so a Small and a Large on the same meal can show different values.