The chart is screwy, it corresponds to the trough concentrations which is the level at the end of a period right before the next shot, which is day 8,15 and 22.

Quote:

---

Mean trough concentrations for the 162 mg weekly group increased from 1.86 µg/mL on day 8 to 2.89 and 3.55 µg/mL on days 15 and 22, respectively. The corresponding values for the 324 mg weekly group were 5.45, 8.50, and 8.75 µg/mL, respectively.

---

Here is a chart for the concentration level and drop.



https://pubmed.ncbi.nlm.nih.gov/20660677/