Help with how to figure out dose cuts

16 days ago I made my first dose drop on sertraline from 50mg to 40mg. I had been using the attached images as a guide. I’ve only been on the drug 7 months. The drop refelected a 3% drop in receptor occupancy but a whopping 20% on mg dose. Should dose cuts be calculated based on how many percentage point receptors you are dropping or by how much mg dose you are taking? There seems to be a lot of different views on this.