四分律行事鈔資持記 3.56

3.56

分品中。初明大衣。正即本位之衣，從謂缺於本衣，用別衣當數。正十八品者，割截揲葉，各有九故。從有六者，七條二品（割揲），五條三品（割揲襵），縵衣一品。正從合論，則二十四品；三衣互為正從，各二十四品，總七十二矣。縵通三者，隨用分故；合為一者，據體同故。《義鈔》缺文，《業疏》具顯。

Under "Distinguishing the Grades": it first explains the great robe (saṅghāṭī). The "primary" is the robe of one's fundamental status; the "secondary" means that when one lacks the fundamental robe, one uses a different robe to serve in its count. There are eighteen primary grades because cut-and-pieced and patched-leaf robes each have nine. There are six secondary grades: two grades of seven-strip robes (cut-and-pieced and patched), three grades of five-strip robes (cut-and-pieced, patched, and pleated), and one grade of seamless robe (mānavastra). Treating the primary and secondary together, there are twenty-four grades; since each of the three robes has its own primary and secondary forms, each has twenty-four grades, totaling seventy-two. That the seamless robe extends to all three is distinguished according to its usage; that they are combined into one is because their substance is identical. The text is missing in the Commentary on the Meaning, but fully revealed in the Karma Commentary.