Thanks Robert!
Yes, it seems that "broad" refers to a generic usage of the keywords throughout the page (document elements & body text).
And for "appropriate" and "exact", here is what I was able to figure out so far, not sure if it is true yet
The "appropriate" refers to keyword usage (not in exact fashion as the keyword phrase) within the document elements such as H1, page title, etc
And "exact keywords" refers to exact keyword usage within the body text.