Well, I see nothing wrong on your screenshot.
Your curve controller output can be scaled, and in your case is likely scaled, so <45% controller output is matched to 58% fan output.
Controller (curve controller etc) is a software algorithm creating output between minimum and maximum you set (30% and 100%), but controller's 30% and 100% can be scaled to e.g. 40% and 100% of fan output.
Take a closer look at this section: