This is an example based on post at: http://excelexperts.com/brackets-in-formulas

Bracketed column name can be seen when you choose "Show Total Row" with Data Table. When you right-click on Data Table and choose "Show Total Row" and choose "SUM", this is what you get within a Total cell. "Meal" within brackets refers to column "Meal" within Data Table, not a named range. So, "SUBTOTAL(109,[meals])" means "SUM of 'Meals' column", where "Meals" is a column within Data Table.

Maybe "Sum" cell was copied away from a Data Table, and that is why it looked strange.

Look at example file attached.