विंशतिवर्षो ग्राह्यः ॥ कZ_०२.३१.०९ ॥
viṃśativarṣo grāhyaḥ
An elephant of twenty years is fit to be taken into state service (accepted for procurement/training).
Set a baseline age-eligibility: accept elephants at about twenty years for state service.
To standardize procurement and reduce risk—very young or very old elephants are less predictable in performance, health, and training outcomes.