HMom16 - I do not know how it works at Penn, but . . . . you might be interested in looking at this from Penn’s Student Records System: https://provider.www.upenn.edu/computing/da/dw/student/srsadmission.e.html
At that website, you will find what is described as the “SRS UNDERGRAD ADMISSIONS Table - Data Element Index.” Since your question is about ED admissions likelihood for a “preferred walk-on” athlete, look in the Table at Athletic_Rating, which says: “The student’s athletic rating established by intercollegiate athletics and undergraduate admissions. Non-athletes will have a rating of NULL. A rating greater than ‘2’ indicates that the students is considered a recruited athlete. Values: NULL; 1-6.”
My best guess at how much does being a preferred walk-on mean during ED, is “1 or 2, and 2 is twice as much as 1.” And, if a “preferred walk-on” gets a 3, because he/she is considered just barely a recruit, that is three times more than one.
My wild speculation, with no evidence to back it up, is that AthleticRating points might get funneled into consideration with the 1-9 AcademicRating and the 1-9 Non-Academic_Rating. Since 18 is a perfect combined Academic + Non-Academic Rating, picking up 2 or 3 extra points would be very valuable (if that is how it works, which I am only guessing).