This button is used to update Start and Finish fields in the Budgets Details Tab Table. When you click the button a confirmation dialog opens:
When you click the OK button the dialog closes and copies the latest Start and Finish dates for the linked task from the project schedule into each line in the table. If there are no linked tasks no lines are updated.
This drop down list creates grouping in the table based on the selected WBS level. The results you see will vary depending on the WBS structure you use. To use this field, select one or more levels in the drop down list and then click the Refresh button to apply the grouping.