Thanks, I am glad you like the app!
The overpull calculation in pianoscope is not based on percentages. It is a custom algorithm which includes the pitches of several neighboured notes with different weights. I currently don't provide a chart for it, but to get a feel of how much overpull pianoscope is calculating, you can simply setup a pitch-raise and step through the range on the onscreen keyboard and check were the overpull marker is on the tuning scale.
