Reference Lines (Bands) are Table Calculations
made on top of their underlying Aggregates
(which in turn could be Table Calcs, too).
So in your case one could grab the formula
from the Percent of Total SUM([Weight]) green pill on Rows
(by double clicking on the pill and copy/paste the calc),
then make a couple of calculated fields in the data schema,
the latter being the 'Max-Min (pp)'.
For the calculation to get the same results as the Ref Line,
the proper Addressing (Compute using) should be set.
Please find the attached.
X_4_percentage_point_YF.twbx 2.5 MB