I hypothesised it might be because it's a 6 cylinder engine (as mentioned in the first post), which the manual discussed. I thought it's somehow confused by the fact they are linked together on one graph when I tried to adjust it - but thinking about it, it was wrong right off the bat - so here's what I did:
First I set the EGT limits on the 10 step scale, and adjusted the top and bottom of scale to get a nice round number 25*C / step in this case.
Then I went to CHT, and straight away I noticed it said 7*C per step = wrong off the bat because the that makes 70*C and the scale was about 180 degrees between top and bottom.
So then I adjusted the top and bottom (as shown in photo). As I reduced the difference from the default values, the calculation counted down from 7*C, 6, 5, 4, etc until it went to zero, then blank for a while, and then it came back at 7299*C / step.
I wanted to get a nice even step 150*C / 10 steps = 15*C each. I cannot run-up the engine right now, so I don't know whether it's working or not.
I will check again tonight, when I get back to the plane.