What is the wisdom behind the martyr having seventy-two houris in Paradise and interceding for seventy of his relatives?

Al-Tirmidhi, Ibn Majah, and Ahmad narrated from Al-Miqdam ibn Ma'dikarib, may Allah be pleased with him, that the Prophet, peace and blessings be upon him, said: "The martyr has six characteristics with Allah: He is forgiven with the first gush of blood, he sees his seat in Paradise, he is protected from the torment of the grave, he is safe from the greatest terror, a crown of dignity is placed upon his head—a single ruby from it is better than the world and all that is in it—he is married to seventy-two wives from the houris with wide, lovely eyes, and he intercedes for seventy of his relatives." The specification of seventy houri may be intended as a precise number rather than for multiplicity. As for the seventy relatives, it may be for multiplicity, and the use of "seventy" to denote a large number is one of the Arabic linguistic styles. And Allah knows best the wisdom behind these numbers.