There are two lines that each appear to represent an advance curve. One starts with 8*BTDC, the other with 12*BTDC. That I get.
I'm afraid I don't get it though… the two lines, what do they represent? I would think that there would be just one advance value, either 8° or 12°, so I don't get there being two lines in the first place (i.e. at idle).
It seems that the two x,y-intercepts scenario is present throughout the range, right? At 1K, it's 12° and 8°; at 2K it's 10 and 22; and at 27K it's 23 and 35. When you say that's not possible, do you mean "having two values for the advance isn't possible," or are the values outside the range you'd expect?
Perhaps the chart is made to accommodate two scenarios: One where the timing is set to 8° at idle, and another where it's set to 12. Then, each of the two curves represents a result starting from one of these values. However, if it were a matter of a simple setting, I would expect the "break" (the point on the X-axis where the curve starts its ascent) to appear at the same RPM for both curves (currently it's at ca. 1600 and 1900). However, I know exactly zilch about how the timing advance occurs on the KLR (or how the ignition system works on this machine at all actually… I'll have to read up on this).
This manual… is it made to cover more than one bike? Two bikes with different ignition systems/timing curves perhaps?