Source settings shows the configuration of chart data source. Can be changed by pressing Edit Data Source button. Please note source type can be changed only for new report. We have created two source types for Trello: Cards and History of cards. Cards source is consists of your current or archived board cards and considered to be used when you suppose to visualize data related to current state of board, for example cards distribution of lists. History of cards consists of transitions between lists. Every raw in datasets of this type is a historical action related to moving card from one list to another. It's considered to be used for visualizing list changes of cards during time in history, for example cumulative, durations or transitions reports.