三彌勒經疏 1.36

1.36

問：何得知諸佛出世唯半劫量？答：雖定文無，而例唯應然。又解：前諸佛出初十劫，最後樓至出第十一劫，至後九劫皆是樓至遺法所被。若作是說，十劫名一劫，對此後十劫且說半劫，義亦無失。

Question: How is it known that the appearance of the Buddhas in the world is only for the duration of half a kalpa? Answer: Although there is no definitive text, by analogy it must simply be so. Another interpretation: The preceding Buddhas appear in the first ten kalpas, and the last, Rucika, appears in the eleventh kalpa, up to the remaining nine kalpas, which are all covered by the bequeathed Dharma of Rucika. If one explains it in this way, ten kalpas are called one kalpa, and in contrast to these latter ten kalpas, it is tentatively called half a kalpa; this meaning is also without fault.