What jon says makes sense tom me, but I must be reading this chart wrong. Not that I doubt you, I just want to learn how to read this correctly for myself. Please point out my errors.
The legend states
"C LR rear lift neg # = lift, pos # = down force on rear end"
For test 10 the whaletail, I read column 4 (CLR) with a value of -.259, and column 12 ( rear lift) as ~-176.
It also looks like the other high downforce "spoilers" had the same negative number trends. Like I said I'm really getting lost.