it isn't quite true that the categories are static, in fact, I've changed them a fair bit as I've reorganized containers. Sometimes I realize that two different containers should really be one container, and when that happens, I'll write down the sum of the dots on the new box label and continue it, so I don't lose the information. Less often, I'll take some parts out of a box and put them in a different one, accepting the loss of partial information. But I generally do that because I notice a subset of parts doesn't really belong in the box, and so the dots weren't really conveying information about those migrated parts anyways. It's more fluid than you might think at first.