The order in which the interaction occurred, in order of most to least recent interaction before the conversion activity. For example, if the conversion occurred at noon, the list of activities leading to the conversion could be numbered 1) 11:55 am, 2) 11:30 am, 3) 9:00 am, 4) previous day, and so on.
Interaction #1 is not necessarily the attributed interaction. For example, let’s say that Interaction #1 was an impression, and your other interactions were clicks. In this case, the conversion would be attributed to the most recent click instead.