The report cards are generated for your keywords (the ones associated with your campaign) that rank in the top 50 positions in the SERPs; the page that is graded is the page that resulted in that term being in that position.
In other words, the fact that you have a report card for a page means that page is already ranking in the top 50 for the term associated with the report.
So if you got a report card for the page that you are optimizing for the phrase "outdoor wedding venues in Las Vegas" and it was associated with the phrase "Las Vegas wedding venues" it means that page is currently ranking in the top 50 for "Las Vegas wedding venues". Even if that isn't the phrase you are specifically trying for, it can be a good thing when a page can rank for multiple variants.
What I like about these reports is that they enable me to see which pages are actually performing for my keywords (sometimes, not the ones I'd expect).
