What is the official recommendation for the length of time Cosmelan 1 should be left on skin type II?

I'm coming up with the widest range of recommendations from doctors between 4-10 hours. That's a tremendous discrepancy! Some insist 4 hours is enough time of action; others (plus patients) have said 4 hours is worthless and needs to be a minimum of 8 hours. What is the official directive from Mesoesthetic for Fitzpatrick type II? Thank you!