http://iscoresports.com/

What is "RPA" on the stats and how is it calucalated?

IIRC, RPA is a measure of runs produced per plate appearance. So it would be runs scored plus runs batted in per plate appearance. I don't remember if home runs are subtracted, to avoid double-counting that as both a run scored and an RBI. I can see arguments both for and against doing that....