I think that the problem is that there is no universal definition as to what constitutes highly, exceptionally, or profoundly gifted. Some of us here have switched to highly gifted+ (HG+) for everything in the 99.9th or close.
As far as the highest scaled score one can receive, it is a 19 without extended norms. With extended norms, which it looks like your tester used, a 28 is as high as it goes. None the less, your ds appears to be very, very gifted and I'd feel free to call it whatever appears to fit the child you have
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