Gauntlet runs represent one player finishing one run. Therefore, they are marked at the moment where the player finishes the last match of the run, regardless of when it started and when individual matches were played.
Only completed gauntlet runs are included. If a player forfeits before completing the run (e.g. drops after going 0-1 in a draft gauntlet), it will not appear in the graph. Therefore, while it takes 8 runs to be equivalent of 1 draft, the actual number might be lower in order to account for forfeited runs (including rare drafts).