Sn 2.1 has been translated as follows:
Ye ariyasaccāni vibhāvayanti, Gambhīrapaññena sudesitāni; Kiñcāpi te honti bhusaṃ pamattā, Na te bhavaṃ aṭṭhamam ādiyanti; Idampi saṅghe ratanaṃ paṇītaṃ, Etena saccena suvatthi hotu
Who clearly comprehend these Noble Truths well-taught by him of wisdom fathomless, however heedless be they afterwards upon an eighth (aṭṭhamam) existence (bhavaṃ) they’ll not seize (ādiyanti). Yea, in the Saṅgha is this glorious gem: By virtue of this truth, may blessing be! (Mills)
Those who have seen clearly the noble truths well-taught by the one of deep discernment — regardless of what [later] might make them heedless — will come to no eighth state of becoming. This, too, is an exquisite treasure in the Sangha. By this truth may there be well-being. (Thanissaro)
Those who realized the Noble Truths well taught by him who is profound in wisdom (the Buddha), even though they may be exceedingly heedless, they will not take an eighth existence (in the realm of sense spheres). This precious jewel is the Sangha. By this (asseveration of the) truth may there be happiness. (Piyadassi)
What is meant here by an "eighth grasping, seizing or taking up (ādiyati) of becoming/existence (bhava)"?