As I read it - looking at the red graph below which I assume is after Audyssey, the sub is at +5dB at 60Hz, then drops 10dB to -5dB at 50Hz, and drops another 12dB to -17dB at 40Hz! Then it spikes a full 15dB to -2dB at 35Hz.
As I read it, the left side of the graph is 20Hz!
I believe each line below 100Hz represents a 10Hz increment.