So for a while I’ve been trying to figure how to know what the secret values mean in the spec editor. Sometime you’ll see 0, –1 or –2 and I had trouble figuring out when those values could be used.
I’ve stumbled over a neat trick. However your mouse over a dimension shows you available values.
We submitted a request to have a ? button placed to pop up the tooltip so that the extra information is easier to get to.