Still can't find an explanation.
A compass rose on any map in the world would look like this:
https://www.google.com/search?q=comp...%3B2400%3B2341
In SH it is opposite (180 at top, 90 at left side).
My assumption is that this is so that a person would find it easier to understand which of the two reciprocal headings one should go for? In your picture there, 245 degrees is the first marking of the compass rose that the rhumb line meets in the desired direction of travel. But in any actual map I've seen, the rose would be opposite, and you'd see 245 degrees on the other side of the compass rose. In other words you'd get your heading off the marking at the point where the rhumb line is 'exiting' the compass rose (in the desired travel direction).
This might be trivial, I can make do with the tool as it is, I just wonder why it was designed in this manner. Probably because it is easier to just draw a line and read the heading at the edge of rose instead of having to draw a line and then put the rose over it to see where it intersects said line.