Let's take a look at the General tab in TMG's Source Definition screen.
|General tab in the Source Definition screen|
|Short Title||Second Location|
|Short Subtitle||Publisher Location|
|Second Person||File Reference|
|Second Date||Film Number|
Take a look at the TMG screenshot. If we were to add the [SHORT TITLE] element to this screen, it would not appear in the first available blank spot (the second label in the second column). It would pop into the first label spot in the first column, and all the rest would move down. If we were to add an element from the Publisher source element group, it would be inserted between our Location element and our Description element, which is defined as part of the Series source element group.
Try it! Let me know if you think I've made an error in this Periodic Table of (Source) Elements. Again, this is of academic interest only. Knowing this won't make any difference in how you use TMG.