G36 Improvement Project

I’m not sure if I’m doing something wrong or misunderstanding something with the mixture, related to this guide: [HOW-TO] Best Practices to Fly Bonanza G36

When cruising, (below 6000ft in this example), I follow the recommendations, leaving my throttle full, and prop 2500. My assumption now is that I adjust lean until it reads 15gph, however adjusting lean does not impact my gph reading in any way. What I’m currently doing to bring gph & KIAS to recommended levels is to adjust MP (which goes against the recommended FULL setting).

Am I missing something here?