All the grand total SUMs generated by AutoSum are Unions, showing each subtotal reference separated by commas. Number-crunching never has been much fun but this certainly better than having to construct Grand Totals from plus signs and cell references.
Our SUM formulas usually contain Range References, using a colon separator. For example, C3:C5 means “from C3 to C5”. Union references use commas. For example, C12, C16 means C12 and C16.