As stated in the August NIH Extramural News:
Need help understanding your summary statement? Help is on the way. NIH will begin requiring reviewers to include a paragraph in their written critiques to explain the factors that informed his or her overall impact score. This change will provide applicants with greater insight into how each reviewer assessed scientific merit of the grant application and determined his/her overall impact score.
Remember, reviewers do not use a defined formula to derive the overall impact score from the individual criterion scores. They are instructed to weigh the different criteria as they see fit in deriving their overall scores.
You will see the additional information in summary statements for applications reviewed this fall.