Make a set of headings for the various functions involved in your job. If it seems worthy, list it as an additional part of your job description. For instance, a rating of 550 might mean that you are well on your way to doing a perfect job, but there are still a few ways you can improve. After giving the rating, provide a written justification for the rating. This should take the form of a few sentences identifying concrete things that you have achieved.
Higher ratings deserve more impressive justifications.
Use short statements of the type that could also be used on a resume.