Microsoft project management software used to plan, manage, and communicate a project schedule and other information among workgroup members, project managers, and other stakeholders.
Kunal Shah DW,
First of all please tell us which version of Project you are using (i.e. desktop, Project Online, Project for the Web, etc.).
We really need to see a screen shot. You should NOT be directly entering any dates. Dates in Project are calculated based on entered duration values and task dependencies. Directly entering dates sets a constraint and essentially defeats Project's ability to dynamically schedule.
Summary lines are NOT tasks, they are simply a summary of data from performance (subtasks) under them. Summary line duration is the working time between the start date of the earliest subtask to the finish date of the latest subtask.
What do you mean by "Duration rounding formula"? There is no "rounding formula" for the normal Duration field. Are you using a custom Duration field (e.g. Duration1)?
What is your Project calendar? Do any of your tasks have a task calendar (i.e. Task Calendar field OTHER than "none")?
By the way, all tasks should be auto-scheduled.
John