Spectate checks the keyword density for all of the pages containing a keyword that you are tracking.
Click on the "Marketing" tab on the left side, and then select Track -> Keyword. This will show you a list of all the keywords that you are currently tracking.
Click a specific keyword, which will take you to the individual keyword's page.
Scroll down to the "Word Densities" section, where you will see a list of all posts and pages that contain the selected keyword. It shows you the number of times that the keyword was mentioned on the page, as well as the density percentage.