Units of measure — Stored canonically, shown in your unit

A value is stored in the unit the column declares — not the class's base unit, and not whatever it happened to be typed in. Type 1200 g into a column held in kilograms and 1.2 is what lands in the cell; the column, its total and its export all read 1.2 kg. That is what makes a column people fill in grams, kilograms and tonnes add up to the right number: the conversion happens once, on the way in, so everything downstream is adding like to like. What you typed is not thrown away. It stays beside the value, seeds the editor when you reopen the cell, and shows on the cell's tooltip — so a row entered as 1200 g still says so. Changing the column's unit later converts the values with it. Move a column from kilograms to grams and every stored number is multiplied through exactly, once, inside the same save — the confirmation tells you how many changed. This is the one config change in RowFold that rewrites records, and it does so because the alternative is worse: leaving them alone would keep the same digits under a new label, silently restating every number by a factor of a thousand. Moving to a unit in a different class is refused instead, because no exact factor exists.