"does not work" is not true, it just doesn't work how you expected. So you already see how it IS working. now maybe if I give you context it will make more sense. I have no idea what you are grouping or why but remember Excel is based in spreadsheets and typically thought of having tables of data. Now assume you have a table of data with sub-totals. Now if you GROUP sections of data (i.e. everything above that sub-total) it will GROUP those lines of data and attach it to the sub-total line so you can hide the details and only look at that sub-total or see all the details. Maybe if you consider that as the expected use scenario you can see why it works as it does.
