where the value printed on the wave was left out for want of room, which is what the hover tooltip is for. Made while drawing, because that is when it is known.

the samples this picture was drawn from, kept so that anything describing what is on screen - the value column, the hover tooltip - reads the same numbers the pixels came from. Not a copy: it points into the array the fetch delivered, which the cache may have replaced with a newer window since. That is exactly why it is kept here rather than looked up again.