The weight for donations in engagement segmentation does not count every individual donation in a sustaining gift thread, rather it counts the entire thread as 1. For example: if a constituent set up a sustaining gift to donate once a month and let it run for 12 months, then the weight would show as 1, even though there were 12 donations. Additionally, the system only counts the first donation in the sustaining gift thread. This means that if the sustaining gifts were instantiated before the timeframe that you specify in the task, then it will show a weight of 0.