The number 40 is middle age, the age of a mature adult. It marks the beginning of one’s career that will reach its peak of success at around age 50. Therefore in spirit, as it relates to being a bureaucrat or a business person, it is the age at which a career is launched. Those who achieve the peak of their professional success at age 24 will find that by age 40, one’s life may embark on another ten years of work in another career, another business, another field of endeavor, etc.
So, regardless of what the specific single digit numbers (4) and (0) symbolizes, the number 40 symbolizes “the age of launching”. In modern Western culture, the age 40 is the beginning of the mid life crisis, and many divorces occur at age 40 for married men.