Thanks, Ben, but an explanation of what NX is doing isn't really what I was looking for. I wanted to know if Development used a specific ASTM, ASME, SAE, ANSI, or ? standard to ensure compliance. If I had to guess, it would be ASTM E29-13. John's original explanation of the behavior was likely from a distant past, as we had this discussion back when I called in about a UG dimensioning problem I was having. I only discovered there actually was a problem back then when I created a new dimension on the left side of something to replace one that I was about to delete from the right side of the same object. The values were different, but they shouldn't have been. This was a very long time ago, possibly before solid modeling. The problem was fixed shortly thereafter and I hardly ever paid attention to the issue after checking for a few versions.