Portion analysis
Serving total and calorie density answer different questions
The listed source amounts run from 85 to 90 grams—a 5-gram gap before composition enters the comparison. Their own source servings run from 72 calories for “canned” to 158 for “cooked.” At a fixed 100 grams, “canned” is 85 calories and “cooked” is 176—a fixed-weight separation of 91 calories. For Tuna, the serving view answers “how much is in the database portion?”; the 100-gram view answers “how concentrated is the matched record?” Neither reveals how many grams were actually eaten.
The scaling rule: multiply a per-100-gram value by eaten grams ÷ 100. The arithmetic is exact; the result is only as defensible as the record match and portion estimate.
Preparation analysis
The long description carries the evidence
The published descriptions distinguish forms such as “tuna, canned”, “tuna, cooked”, and “tuna, raw”. The source formulations contain 4 distinct ingredient codes; examples that appear in only part of the set include fish, tuna, fresh, yellowfin, raw, fish, tuna, light, canned in water, drained solids, oil or table fat, nfs, and salt, table. On this Tuna page, those rows make the records inspectable, but they are not a controlled experiment: they cannot tell us that one named input, by itself, caused a nutrient difference.
Database precision is not meal certainty. Retain the exact description beside the number so later corrections remain possible.