What's the deal with multiple background properties in a double nested list in the CSS Properties task pane?

Here's an question I got from a reader.  This came up in Expression Web 2 Step by Step, CH7 page 168 step 9: 

Question:

...ALSO, I am very confused with the CSS task pane. There are TWO background-image places and no indication of which I should be using. I used the one that required expansion (+ sign) as instructed in Step 7, but am I supposed to keep using that background-image for the rest of the steps?

Answer:

If you expand a property in the CSS Properties task pane, and there's another group that you can expand within the parent stack, that's where you can enter "short-hand" CSS.

See this video for clarification:

If the Silverlight Player below isn't big enough click here for a raw video in .WMV.