俱舍論疏 12.42

12.42

論「所餘成壞至二十中劫」，此明准住二十時量，成、壞、空劫量同也。空之一劫更無別相，故不別釋。

On the Śāstra's text, "The remaining [kalpas of] formation and destruction... twenty intermediate kalpas": This explains that, following the temporal measure of the twenty of abiding, the measures of the kalpas of formation, destruction, and emptiness are identical. The single kalpa of emptiness has no further distinctive characteristics, and therefore is not separately explained.