俱舍論記 18.184

18.184

「解脫涅槃至義准已成」者，釋第四句，明解脫異名。解脫涅槃，亦名無上，以無一法能勝涅槃。是善、是常，超眾法故，尚無有法與涅槃等，況有上者。餘法有上，義准已成。即一切有為、虛空、非擇滅，由非具前善、常相故，隨其所應皆名有上。

Regarding "Liberation, nirvāṇa [...] is already implicitly established": this explains the fourth line, elucidating the alternative designations for liberation. Liberation, nirvāṇa, is also called "unsurpassed" (anuttara), because no single phenomenon can surpass nirvāṇa. Because it is wholesome and eternal, transcending all phenomena, there is not even any phenomenon equal to nirvāṇa, let alone superior to it. That the remaining phenomena are "surpassed" (sottara) is already implicitly established: namely, all saṃskṛta [phenomena], space (ākāśa), and non-analytical cessation (apratisaṃkhyā-nirodha), because they do not possess the aforementioned characteristics of being wholesome and eternal, are all called "surpassed" according to their respective nature.