The 57/08 is notoriously all over the map. I have a non etched bridge in my McC that reads about the same as yours (7.9), and another non etched version that reads about 8.5. I reached out to customer service and suggested they might have accidentally put a neck PU in the bridge, but I was given to understand it is within tolerances.
I think that is kind of weird, especially since the specs seem to be around what you quote. Both of my bridge PUs were most likely made within a month of each other (serial nrs of the guitars) and are the early early versions. I doubt they did a revision within that time frame, withing a couple of months after launch, but that is up to PRS I guess. Consistency is one of the many great things about PRS, but the 57/08 is quite the exception.
Guitars sound great by the way, and the lower output one suits the McC very well.