iOS Why do size inspector constraint constants

This is a minor issue but I haven't discovered the secret. I'm using Xcode 5.

When I select a view in a storyboard, the Size Inspector displays its list of constraints. For each constraint you see the type of constraint and the target, and sometimes you see the constant too.

Why only sometimes?

That's a perfectly plausible explanation, Duncan, especially since they've redesigned the constraint system.

Still, there's probably some deterministic way to make the constants display. I just can't figure out what it is. It's much more convenient to go over the constraints I've set when the constants are shown, rather than having to open each one individually or use up screen space by displaying the Document Outline.