Double the number of targets, the duration, the range, etc...
But, no, Double does not allow for adding a scaling option (and the Doubling of a range or duration from a casting roll is NOT a scaling, is is a doubling of whatever the range of the spell, at the time of casting, was.
Thus, if a spell has a range of 50', then Doubling would make it 100'. If this same spell had its range scaled to be 100', then it is doubled to 200', etc...