How new paragraph style picks up attributes (and applies them)

I am puzzled by the way a paragraph style created from existing text picks up its attributes.
I have attached a file with an example (PDF with AI editing preserved). There are five lines of text.

Column 2:
Line 0 is the Normal Paragraph Style.
Line 1 is the Normal Paragraph Style with font size increased to 18 pt and first character Horizontal Scale set to 50%.
Line 2 is the Normal Paragraph Style with font size increased to 18 pt and last character Horizontal Scale set to 50%.
Line 3 is the Normal Paragraph Style with font size increased to 18 pt.
Line 4 is the Normal Paragraph Style with font size increased to 18 pt and middle character Horizontal Scale set to 50%.

I select the entire text in Column 2 and use it to create the corresponding paragraph style (name in column 4). I do that with "New Paragraph Style" while the text is selected. For each line, I then copy thext "1" (in column 1), change it to "DEF", and apply the corresponding new style to text in Column 3.

1- I don't understand why the text to which I apply the style comes with a + sign after the style name for lines 1-4.
2- I don't understand why the new paragraph style doesn't ignore the Horizontal scaling since it has mixed values (in lines 1, 2, and 4). I expected the new paragraph style like pstyle3 to have a blank value for Horizontal Scale since that is how it appears in the Character Panel when I select the entire text. Instead, the paragraph style shows 50%.
3- When I first apply the new style to "DEF", it appears with + next to it! If I apply it a second time, it fully takes effect. I would expect this to happen the first time I apply the style.

4- When there is a + sign next to a paragraph style, is there a way to tell which attributes have changed (like in InDesign)? Or is the only way to find out to compare each attribute value to the original paragraph style?

This is for CS4. Thanks.