Shraddha does not only gratify one's ancestors. A person who performs Shraddha as per proper rituals and according to their means brings satisfaction to all beings, from Brahma to grass. - Brahma Purana
As per Vedic Astronomy, there are 27 constellations in the zodiac. Each constellation has got 4 quarters. 24 X 7 = 108. If you repeat a mantra 108 times, it covers the entire zodiac and gives immense benefits.