You buy a cushion online and the listing gives you three numbers. 19, 21, 23. Nothing on the page shows you what they look like on a face. So you take 21, because 21 is the one everybody seems to mention, and it turns up half a tone off. The usual explanation is that the brand ran light. Sometimes it did. More often the number was never a measurement in the first place. No two Korean brands sat down and calibrated their 21 against each other. Korean base makeup has used this numbering for decades and...