Hi Annika,
What is the Data format setting for cells in column E of your table?
Try setting it to Number, with Decimal left at Automatic and negative numbers left at their default setting.
Your formula looks correct, although I would have converted the row containing it (row 10) to a Footer row, then used this simpler version of the same formula:
SUM(E)
The E reference is to all cells in column E, except cells that are in a Header row and cells that are in a Footer row. As you add more rows to the table (if needed), they are automatically included in the SUM(E) calculations.
Regards,
Barry