This returns the value 314:30:00 for my Grand Total.
Digging deeper into my problem, this is what I found:
The Hours column has the formula: =B1-A1 etc.,
Specific Cells on Subtotal column have the formula: =Sum(C1:C3) with Format
The last cell on the Subtotal Column has the formula: =Sum(C1:C33) with
I introduced values in a new column (Col E) where the values in this column
= Col D. Now when I sum Col D into Grand Total with Format [hh]:m it totals
up correctly to 26:30.
How would you fix this without using Column M?