I've completed exalt 6 8 times, so according to the description, I should get a red bar reduction of 2*8 = 16%. As the max red bar size is 1e6, this should give me a red bar of 840e3, but I get a red bar of 920e3 instead.
Not sure if I'm understanding something wrong, or if this is a bug, but a quick reading of the source appears to agree with my interpretation, which makes me even more confused.