What is the Manually Scheduled Summary Task Roll-up Bar?
In Project 2010 supports Top Down Scheduling. You can define the duration of a summary task, rather than have Project calculate for you. When you enter a manually scheduled summary task, you can choose to enter the duration you want it to take, and a small blue bar appears under the summary task bar.
This represents the roll-up of the duration of the subtasks, and provides a visual way of indicating whether you have contingency time. If you change the durations of the subtasks so they take longer, the subtasks will end up exceeding the original duration of the summary phase. In this case, the roll-up bar will turn red indicating you now have a problem.