I'm sorry for the confusion with the Timesheet screen.
Timesheet shows all items which have an iteration and this iteration has time interval which contains the current week or part of it. In other words if you have a long iteration which continues many weeks and you add items to it the timesheet will show all these items. You can try to reduce the time-span of the iteration to less time (two weeks for example).
Also if you change an iteration of Bug or Story, all tasks but these marked as Done or Deleted change there iteration. So all the Task marked as Done or Deleted do not change there iteration. This behavior is needed in order the Reports to generate correct data.
If this information doesn't help you don't hesitate to contact us again.