金剛般若經依天親菩薩論贊略釋秦本義記卷上 1.125

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經。須菩提言甚多世尊　第二答也。此中所言甚者。即以世界至大微塵極少破麁為細塵即無邊多義難量故言甚也。

[Sūtra:] "Subhūti said: 'Extremely many, Bhagavat.'"
This is the second [part], the answer. What is here called "extremely" means that since a world-system is utmost in greatness and a mote of dust is utmost in smallness, breaking the coarse into fine dust results in boundless multiplicity whose meaning is difficult to measure; hence he says "extremely".