The star rating on the leaderboard is a way for users to know if they have been uploading quality images. 

When an image is uploaded it is automatically sent through the transcription process where it receives a rating. The stars show how transcribers have rated your uploaded images. Top-quality images receive 5 stars.

The rating on the transcription page is done by clicking on the red flag in the transcription process. 

For more information click on this article: How can I rate an image while transcribing?

From the BillionGraves Website:

#1 Log in to 

#2 Click on Leaderboard.

If you have a rating with one or two stars, do not worry! Go to My Stats and look for the reasons your images were rated poorly. You can clean them up by clicking on the reasons listed and re-transcribing them. This will allow you to earn back your shiny five-star rating!

You can find the link to the leaderboard on the left side of your dashboard page: 

Your star rating is at the top of the leaderboard.

Or you could click here: to view the "My Statistics" page.