Nothing is attached?
There is no reverse order that I know of. Simply set yplot:=0-y then plot x vs yplot..
Or export to excel to plot.
This is what the OP wants (the plot to the right), as I understand it:
This is easily accomplished in ANY version of Mathcad
It's just NOT supported by (any version of) Prime, because Prime refuses to set the upper y-axis scale limit to a smaller value than the lower limit: