Are Ascending and Descending Intervals Calculated?

Descending intervals are calculated the same way as ascending intervals and the construction of the scale does not change, so we determine size and quality using the same method.

Are intervals the same ascending and descending?

When the second note of an interval is higher than the first note the interval is an ascending interval. If the second note is lower the interval is a descending interval.

When calculating intervals both the start and end note should be included in the count?

Descending intervals are calculated differently from ascending ones. The two notes of an octave sound exactly the same due to the simple relationship of their frequencies. When calculating intervals, both the start and end notes should be included in the count.