I learn with a group of people each week and we take turns leading. I need a lot of time to prepare and usually start a week in advance. I read and review multiple times during the week. If I am tasked with leading the group in a week when I will complete the masechta, do I make the hadran when I finish my first run through or at any other time (such as a few runs later when I feel I understand the content) or do I wait until I "finish" with the group even though this might be the 5th time I am going through the same section?
This becomes an issue if I am going to lead on a date which is within the 9 days and then host a siyum. If my prep has me complete the masechta before the 9 days begin but the group convenes during the nine days have I "finished" during the nine days or before them?