It is unclear what it is you want to do. The plot shown is a plot of the kernel density estimates of the PDF (the area under each curve is 1).
If you want the Y-axis to be in percent, right-click the axis and change the format to percent.
If want all of the response values be on a common percent scale, e.g.
Y_scaled = (Y - Low L) / (High L - Low L), then you should do that transformation in the data table and then run the analysis on the scaled variable.