Thank you for your reply.

The selected cell range has no effect on the values or the appearance of the "New Formatting Rule" dialog window.

The text fields for the minimum and maximum value (both labelled 'Value') contain greyed text "(Lowest value)" and "(Highest value)" respectively.

I find it hard to believe that these are not intended to be edited. If that was the case there would be no reason for the group select icon to exist.

Thank you