For each team, the bars indicate the number of commits during the current period, the net number of lines added and the net number of lines removed. Here, "net" refers to differences between the last state of a branch in the team's repository (on cs164-taa) just before the starting date and the current state. Thus, lines that are added and then removed do not show up. Lines that are replaced or moved count as both an add and a deletion. The chart only shows lines for teams that showed activity in the indicated period and branch.