Hi, Afarag!
It's the table total line feature that comes with Excel. Do this:
a) Create a new workbook, type titles for A & B columns, and fill a few rows with numbers, like date and amount.
b) Go to Insert tab, Tables group, Table, and create a new one from the data entered in a)
c) Click on any cell of the new table and an overlapping Table Tools ribbon will appear at the right of the Excel option ribbon.
d) Go to Table Style Options and click on Total Row.
... et voilà, c'est tout!
Regards!