This is an open label study which doesn't take into account the placebo effect (which we know is a large factor in depression, about 75% of the effect of antidepressants). This study even mentions that other placebo-controlled trials showed no effect in depression between placebo and microdosing.

Typical cohen's d effect size of antidepressants is 0.3. If the placebo is 75% of the response, that means a drug placebo has a d value of about 0.9. This study shows a d value of 0.39 for depression, which means it has about half the effect that we would expect to see simply from the placebo effect. So, either it is a very poor placebo, or the active ingredient has a negative effect on depression, or the participants weren't very depressed in the first place, or (more likely) we simply don't have a clue what the effectiveness actually is.