There is a difference between acinteyya and asaṅkheyyā.
- Acinteyya means a concept is “not amenable/graspable to average humans.” Such things can be discovered/explored only by a Buddha.
- Asaṅkheyyā specifically refers to the inability to express the magnitude of an entity with numbers. The Buddha states that the length of a maha kappa cannot be expressed in numbers. That could be because the number system at that time was not big enough to express that number, and/or the length of a maha kappa could change somewhat each time.
