Picture this: you create a new timesheet in Project Web Access, and rather than seeing a blank timesheet, as you might expect, you see a timesheet prepopulated with Actual Work hours. But your project plan doesn't have any Actual Work! Where did the prepopulated hours come from?
The most likely answer is that the tasks on your timesheet have been included on the My Tasks page, and Actual Work was recorded as part of reporting the status of the tasks. If you record Actual Work on a task as part of the task status, when you include that task on a new timesheet, Project Web Access automatically includes the reported Actual Work on the timesheet, regardless of whether it has been saved to the project plan.
Another possible answer is that you had previously created a timesheet and reported Actual Work, then deleted that timesheet. When you re-create the same timesheet, the Actual Work reported on the previously deleted timesheet appears on the new timesheet.
For more information on creating timesheets and reporting task status, see the following help topics: