What does the divided income number signify?

Why is Wolf’s gravestone good?

Wolf’s Gravestone is a 5-Star Claymore in Genshin Impact.
Wolf’s Gravestone Information.

Wolf’s Gravestone
Bonus Effect	ATK + 10.8%
Skill	Wolfish Tracker ・Increases ATK by 20%. On hit, attacks against enemies with less than 30% HP increases all party members’ ATK by 40% for 12s. Can only occur once every 30s.