I have a spreadsheet where the sum function returns the wrong answer. If I highlight the cell range the correct answer is displayed in the status bar. This only happens in columns W and X. Is there some new bug in Excel?
I realise that the screen shot is not ideal, but I cannot install any software like xlsbb.It is hard to say, as you have not shown us your sum formula, nor the data ranges it is looking at.
And we have no idea what columns and rows we are looking at based on your screen print.
But be careful NOT to include dates in your sum range, as dates are actually stored in Excel as numbers (specifically, the number of days since 1/0/1900).
So including cells with dates in them in your sum range would mess up your totals.