I'm reading about the theory behind intervals, and Wikipedia says:
A compound interval is an interval spanning more than one octave.
Does "spanning" in this case refer to the number of staff positions or to the number of semitones?
Wikipedia lists the diminished ninth (12 semitones) as the smallest compound interval, so I'm guessing that the distinction between simple and compound intervals is based on staff positions instead of semitones: intervals encompassing 8 or less staff positions are simple, those with more are compound. Hence a double augmented ninth would still be a compound interval, whereas the doubly augmented seventh mentioned in the title would be simple.
Is my understanding correct?